[Middleware] Move to GenericHost (#23626)

src/Middleware/CORS/test/UnitTests/CorsMiddlewareTests.cs

@@ -10,6 +10,7 @@ using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging.Abstractions;
 using Microsoft.Extensions.Options;
 using Moq;
@@ -27,7 +28,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
         public async Task CorsRequest_MatchesPolicy_OnCaseInsensitiveAccessControlRequestMethod(string accessControlRequestMethod)
         {
             // Arrange
-            var hostBuilder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseCors(builder =>
@@ -39,8 +44,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
                         });
                     })
                     .ConfigureServices(services => services.AddCors());
+                }).Build();
 
-            using (var server = new TestServer(hostBuilder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 // Act
                 // Actual request.
@@ -60,7 +68,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
         public async Task CorsRequest_MatchPolicy_SetsResponseHeaders()
         {
             // Arrange
-            var hostBuilder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseCors(builder =>
@@ -74,8 +86,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
                         });
                     })
                     .ConfigureServices(services => services.AddCors());
+                }).Build();
 
-            using (var server = new TestServer(hostBuilder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 // Act
                 // Actual request.
@@ -102,7 +117,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
             policy.Origins.Add(OriginUrl);
             policy.Methods.Add("PUT");
 
-            var hostBuilder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseCors("customPolicy");
@@ -118,8 +137,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
                             options.AddPolicy("customPolicy", policy);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(hostBuilder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 // Act
                 // Preflight request.
@@ -144,7 +166,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
             policy.Headers.Add("Header1");
             policy.ExposedHeaders.Add("AllowedHeader");
 
-            var hostBuilder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseCors("customPolicy");
@@ -160,8 +186,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
                             options.AddPolicy("customPolicy", policy);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(hostBuilder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 // Act
                 // Preflight request.
@@ -202,7 +231,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
                 .AllowCredentials()
                 .Build();
 
-            var hostBuilder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseCors("customPolicy");
@@ -218,8 +251,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
                             options.AddPolicy("customPolicy", policy);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(hostBuilder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 // Act
                 // Preflight request.
@@ -260,7 +296,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
         public async Task PreFlightRequest_DoesNotMatchPolicy_SetsResponseHeadersAndReturnsNoContent()
         {
             // Arrange
-            var hostBuilder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseCors(builder =>
@@ -274,8 +314,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
                         });
                     })
                     .ConfigureServices(services => services.AddCors());
+                }).Build();
 
-            using (var server = new TestServer(hostBuilder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 // Act
                 // Preflight request.
@@ -288,13 +331,19 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
                 Assert.Equal(HttpStatusCode.NoContent, response.StatusCode);
                 Assert.Empty(response.Headers);
             }
+
+            await host.StartAsync();
         }
 
         [Fact]
         public async Task CorsRequest_DoesNotMatchPolicy_DoesNotSetHeaders()
         {
             // Arrange
-            var hostBuilder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseCors(builder =>
@@ -308,8 +357,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
                         });
                     })
                     .ConfigureServices(services => services.AddCors());
+                }).Build();
 
-            using (var server = new TestServer(hostBuilder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 // Act
                 // Actual request.
@@ -387,7 +439,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
         public async Task PreFlight_MatchesDefaultPolicy_SetsResponseHeaders()
         {
             // Arrange
-            var hostBuilder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseCors();
@@ -417,8 +473,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
                             });
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(hostBuilder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 // Act
                 // Preflight request.
@@ -453,7 +512,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
         public async Task CorsRequest_SetsResponseHeaders()
         {
             // Arrange
-            var hostBuilder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseCors(builder =>
@@ -468,8 +531,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
                         });
                     })
                     .ConfigureServices(services => services.AddCors());
+                }).Build();
 
-            using (var server = new TestServer(hostBuilder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 // Act
                 // Actual request.
@@ -506,7 +572,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
         {
             // Arrange
             var exceptionSeen = true;
-            var hostBuilder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         // Simulate ExceptionHandler middleware
@@ -537,8 +607,11 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
                         });
                     })
                     .ConfigureServices(services => services.AddCors());
+                }).Build();
 
-            using (var server = new TestServer(hostBuilder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 // Act
                 // Actual request.

src/Middleware/CORS/test/testassets/CorsMiddlewareWebSite/Startup.cs

@@ -1,9 +1,11 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 
 namespace CorsMiddlewareWebSite
 {
@@ -19,15 +21,19 @@ namespace CorsMiddlewareWebSite
             app.UseCors(policy => policy.WithOrigins("http://example.com"));
             app.UseMiddleware<EchoMiddleware>();
         }
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .UseKestrel()
                     .UseIISIntegration()
-                .UseStartup<Startup>()
+                    .UseStartup<Startup>();
+                })
                 .Build();
 
-            host.Run();
+            return host.RunAsync();
         }
     }
 }

src/Middleware/ConcurrencyLimiter/sample/Startup.cs

@@ -33,13 +33,17 @@ namespace ConcurrencyLimiterSample
             });
         }
 
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            new WebHostBuilder()
+            return new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .UseKestrel()
-                .UseStartup<Startup>()
+                    .UseStartup<Startup>();
+                })
                 .Build()
-                .Run();
+                .RunAsync();
         }
     }
 }

src/Middleware/Diagnostics.EntityFrameworkCore/test/FunctionalTests/DatabaseErrorPageMiddlewareTest.cs

@@ -17,6 +17,7 @@ using Microsoft.AspNetCore.Testing;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 using Xunit;
 
@@ -27,10 +28,19 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
         [Fact]
         public async Task Successful_requests_pass_thru()
         {
-            var builder = new WebHostBuilder().Configure(app => app
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
+                    .Configure(app => app
                     .UseDatabaseErrorPage()
                     .UseMiddleware<SuccessMiddleware>());
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             HttpResponseMessage response = await server.CreateClient().GetAsync("http://localhost/");
 
@@ -53,10 +63,19 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
         [Fact]
         public async Task Non_database_exceptions_pass_thru()
         {
-            var builder = new WebHostBuilder().Configure(app => app
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
+                    .Configure(app => app
                     .UseDatabaseErrorPage()
                     .UseMiddleware<ExceptionMiddleware>());
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var ex = await Assert.ThrowsAsync<InvalidOperationException>(async () =>
                 await server.CreateClient().GetAsync("http://localhost/"));
@@ -82,7 +101,8 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
         {
             using (var database = SqlTestStore.CreateScratch())
             {
-                TestServer server = SetupTestServer<BloggingContext, DatabaseErrorButNoMigrationsMiddleware>(database);
+                using var host = await SetupServer<BloggingContext, DatabaseErrorButNoMigrationsMiddleware>(database);
+                using var server = host.GetTestServer();
                 var ex = await Assert.ThrowsAsync<DbUpdateException>(async () =>
                     await server.CreateClient().GetAsync("http://localhost/"));
 
@@ -114,7 +134,8 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
         {
             using (var database = SqlTestStore.CreateScratch())
             {
-                TestServer server = SetupTestServer<BloggingContext, NoMigrationsMiddleware>(database);
+                using var host = await SetupServer<BloggingContext, NoMigrationsMiddleware>(database);
+                using var server = host.GetTestServer();
                 HttpResponseMessage response = await server.CreateClient().GetAsync("http://localhost/");
 
                 Assert.Equal(HttpStatusCode.InternalServerError, response.StatusCode);
@@ -142,13 +163,13 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
         [ConditionalFact]
         [OSSkipCondition(OperatingSystems.Linux)]
         [OSSkipCondition(OperatingSystems.MacOSX)]
-        public void No_exception_on_diagnostic_event_received_when_null_state()
+        public async Task No_exception_on_diagnostic_event_received_when_null_state()
         {
             using (var database = SqlTestStore.CreateScratch())
             {
-                using (var server = SetupTestServer<BloggingContext, NoMigrationsMiddleware>(database))
+                using (var server = await SetupServer<BloggingContext, NoMigrationsMiddleware>(database))
                 {
-                    using (var db = server.Host.Services.GetService<BloggingContext>())
+                    using (var db = server.Services.GetService<BloggingContext>())
                     {
                         db.Blogs.Add(new Blog());
 
@@ -172,7 +193,8 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
         {
             using (var database = SqlTestStore.CreateScratch())
             {
-                TestServer server = SetupTestServer<BloggingContextWithMigrations, PendingMigrationsMiddleware>(database);
+                using var host = await SetupServer<BloggingContextWithMigrations, PendingMigrationsMiddleware>(database);
+                using var server = host.GetTestServer();
                 HttpResponseMessage response = await server.CreateClient().GetAsync("http://localhost/");
 
                 Assert.Equal(HttpStatusCode.InternalServerError, response.StatusCode);
@@ -208,7 +230,8 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
         {
             using (var database = SqlTestStore.CreateScratch())
             {
-                TestServer server = SetupTestServer<BloggingContextWithPendingModelChanges, PendingModelChangesMiddleware>(database);
+                using var host = await SetupServer<BloggingContextWithPendingModelChanges, PendingModelChangesMiddleware>(database);
+                using var server = host.GetTestServer();
                 HttpResponseMessage response = await server.CreateClient().GetAsync("http://localhost/");
 
                 Assert.Equal(HttpStatusCode.InternalServerError, response.StatusCode);
@@ -245,7 +268,8 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
         {
             using (var database = SqlTestStore.CreateScratch())
             {
-                TestServer server = SetupTestServer<BloggingContextWithMigrations, ApplyMigrationsMiddleware>(database);
+                using var host = await SetupServer<BloggingContextWithMigrations, ApplyMigrationsMiddleware>(database);
+                using var server = host.GetTestServer();
                 var client = server.CreateClient();
 
                 var expectedMigrationsEndpoint = "/ApplyDatabaseMigrations";
@@ -302,7 +326,11 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
 
             using (var database = SqlTestStore.CreateScratch())
             {
-                var builder = new WebHostBuilder()
+                using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseDatabaseErrorPage(new DatabaseErrorPageOptions
@@ -317,7 +345,11 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
                         services.AddDbContext<BloggingContextWithMigrations>(
                             optionsBuilder => optionsBuilder.UseSqlite(database.ConnectionString));
                     });
-                var server = new TestServer(builder);
+                }).Build();
+
+                await host.StartAsync();
+
+                var server = host.GetTestServer();
 
                 HttpResponseMessage response = await server.CreateClient().GetAsync("http://localhost/");
 
@@ -335,7 +367,11 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
         {
             var logProvider = new TestLoggerProvider();
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseDatabaseErrorPage();
@@ -344,7 +380,11 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
                         app.ApplicationServices.GetService<ILoggerFactory>().AddProvider(logProvider);
 #pragma warning restore CS0618 // Type or member is obsolete
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             try
             {
@@ -391,7 +431,8 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
             {
                 var logProvider = new TestLoggerProvider();
 
-                var server = SetupTestServer<BloggingContextWithSnapshotThatThrows, ExceptionInLogicMiddleware>(database, logProvider);
+                using var host = await SetupServer<BloggingContextWithSnapshotThatThrows, ExceptionInLogicMiddleware>(database, logProvider);
+                using var server = host.GetTestServer();
 
                 try
                 {
@@ -430,7 +471,8 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
         {
             using (var database = SqlTestStore.CreateScratch())
             {
-                TestServer server = SetupTestServer<BloggingContext, WrappedExceptionMiddleware>(database);
+                using var host = await SetupServer<BloggingContext, WrappedExceptionMiddleware>(database);
+                using var server = host.GetTestServer();
                 HttpResponseMessage response = await server.CreateClient().GetAsync("http://localhost/");
 
                 Assert.Equal(HttpStatusCode.InternalServerError, response.StatusCode);
@@ -461,10 +503,14 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
             }
         }
 
-        private static TestServer SetupTestServer<TContext, TMiddleware>(SqlTestStore database, ILoggerProvider logProvider = null)
+        private static async Task<IHost> SetupServer<TContext, TMiddleware>(SqlTestStore database, ILoggerProvider logProvider = null)
             where TContext : DbContext
         {
-            var builder = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseDatabaseErrorPage();
@@ -482,8 +528,11 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
                     {
                         services.AddDbContext<TContext>(optionsBuilder => optionsBuilder.UseSqlite(database.ConnectionString));
                     });
+                }).Build();
 
-            return new TestServer(builder);
+            await host.StartAsync();
+
+            return host;
         }
 
         private static UrlEncoder _urlEncoder = UrlEncoder.Default;

src/Middleware/Diagnostics.EntityFrameworkCore/test/FunctionalTests/MigrationsEndPointMiddlewareTest.cs

@@ -18,6 +18,7 @@ using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.Migrations;
 using Microsoft.EntityFrameworkCore.Storage;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
@@ -27,10 +28,19 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
         [Fact]
         public async Task Non_migration_requests_pass_thru()
         {
-            var builder = new WebHostBuilder().Configure(app => app
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
+                    .Configure(app => app
                     .UseMigrationsEndPoint()
                     .UseMiddleware<SuccessMiddleware>());
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             HttpResponseMessage response = await server.CreateClient().GetAsync("http://localhost/");
 
@@ -75,7 +85,11 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
 
                 var path = useCustomPath ? new PathString("/EndPoints/ApplyMyMigrations") : MigrationsEndPointOptions.DefaultPath;
 
-                var builder = new WebHostBuilder()
+                using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         if (useCustomPath)
@@ -97,7 +111,11 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
                             options.UseSqlite(database.ConnectionString);
                         });
                     });
-                var server = new TestServer(builder);
+                }).Build();
+
+                await host.StartAsync();
+
+                var server = host.GetTestServer();
 
                 using (var db = BloggingContextWithMigrations.CreateWithoutExternalServiceProvider(optionsBuilder.Options))
                 {
@@ -128,12 +146,20 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
         [Fact]
         public async Task Context_type_not_specified()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseMigrationsEndPoint();
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var formData = new FormUrlEncodedContent(new List<KeyValuePair<string, string>>());
 
@@ -148,12 +174,20 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
         [Fact]
         public async Task Invalid_context_type_specified()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseMigrationsEndPoint();
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var typeName = "You won't find this type ;)";
             var formData = new FormUrlEncodedContent(new List<KeyValuePair<string, string>>
@@ -172,10 +206,18 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
         [Fact]
         public async Task Context_not_registered_in_services()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app => app.UseMigrationsEndPoint())
                     .ConfigureServices(services => services.AddEntityFrameworkSqlite());
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var formData = new FormUrlEncodedContent(new List<KeyValuePair<string, string>>
                 {
@@ -197,7 +239,11 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
         {
             using (var database = SqlTestStore.CreateScratch())
             {
-                var builder = new WebHostBuilder()
+                using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app => app.UseMigrationsEndPoint())
                     .ConfigureServices(services =>
                     {
@@ -206,7 +252,11 @@ namespace Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.Tests
                             optionsBuilder.UseSqlite(database.ConnectionString);
                         });
                     });
-                var server = new TestServer(builder);
+                }).Build();
+
+                await host.StartAsync();
+
+                var server = host.GetTestServer();
 
                 var formData = new FormUrlEncodedContent(new List<KeyValuePair<string, string>>
                     {

src/Middleware/Diagnostics/test/FunctionalTests/TestFixture.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
@@ -6,12 +6,14 @@ using System.Net.Http;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.AspNetCore.Testing;
+using Microsoft.Extensions.Hosting;
 
 namespace Microsoft.AspNetCore.Diagnostics.FunctionalTests
 {
     public class TestFixture<TStartup> : IDisposable
     {
         private readonly TestServer _server;
+        private readonly IHost _host;
 
         public TestFixture()
         {
@@ -20,10 +22,16 @@ namespace Microsoft.AspNetCore.Diagnostics.FunctionalTests
             // (DefaultRequestCulture) is consistent regardless of system configuration or personal preferences.
             using (new CultureReplacer())
             {
-                var builder = new WebHostBuilder()
+                _host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .UseStartup(typeof(TStartup));
+                }).Build();
 
-                _server = new TestServer(builder);
+                _host.Start();
+                _server = _host.GetTestServer();
             }
 
             Client = _server.CreateClient();
@@ -36,6 +44,7 @@ namespace Microsoft.AspNetCore.Diagnostics.FunctionalTests
         {
             Client.Dispose();
             _server.Dispose();
+            _host.Dispose();
         }
     }
 }

src/Middleware/Diagnostics/test/UnitTests/DeveloperExceptionPageMiddlewareTest.cs

@@ -11,6 +11,7 @@ using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Diagnostics
@@ -22,7 +23,11 @@ namespace Microsoft.AspNetCore.Diagnostics
         {
             // Arrange
             DiagnosticListener diagnosticListener = null;
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         diagnosticListener = app.ApplicationServices.GetRequiredService<DiagnosticListener>();
@@ -32,7 +37,11 @@ namespace Microsoft.AspNetCore.Diagnostics
                             throw new Exception("Test exception");
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var listener = new TestDiagnosticListener();
             diagnosticListener.SubscribeWithAdapter(listener);
 
@@ -50,7 +59,11 @@ namespace Microsoft.AspNetCore.Diagnostics
         public async Task ErrorPageWithAcceptHeaderForHtmlReturnsHtml()
         {
             // Arrange
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseDeveloperExceptionPage();
@@ -59,7 +72,11 @@ namespace Microsoft.AspNetCore.Diagnostics
                             throw new Exception("Test exception");
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             // Act
             var client = server.CreateClient();
@@ -77,7 +94,11 @@ namespace Microsoft.AspNetCore.Diagnostics
         public async Task ErrorPageWithoutAcceptHeaderForHtmlReturnsPlainText()
         {
             // Arrange
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseDeveloperExceptionPage();
@@ -86,7 +107,11 @@ namespace Microsoft.AspNetCore.Diagnostics
                             throw new Exception("Test exception");
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             // Act
             var response = await server.CreateClient().GetAsync("/path");
@@ -102,7 +127,11 @@ namespace Microsoft.AspNetCore.Diagnostics
         public async Task ExceptionPageFiltersAreApplied()
         {
             // Arrange
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<IDeveloperPageExceptionFilter, ExceptionMessageFilter>();
@@ -115,7 +144,11 @@ namespace Microsoft.AspNetCore.Diagnostics
                             throw new Exception("Test exception");
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             // Act
             var response = await server.CreateClient().GetAsync("/path");
@@ -128,7 +161,11 @@ namespace Microsoft.AspNetCore.Diagnostics
         public async Task ExceptionFilterCallingNextWorks()
         {
             // Arrange
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<IDeveloperPageExceptionFilter, PassThroughExceptionFilter>();
@@ -143,20 +180,30 @@ namespace Microsoft.AspNetCore.Diagnostics
                             throw new Exception("Test exception");
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             // Act
             var response = await server.CreateClient().GetAsync("/path");
 
             // Assert
             Assert.Equal("Bad format exception!", await response.Content.ReadAsStringAsync());
+
+            await host.StartAsync();
         }
 
         [Fact]
         public async Task ExceptionPageFiltersAreAppliedInOrder()
         {
             // Arrange
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<IDeveloperPageExceptionFilter, AlwaysThrowSameMessageFilter>();
@@ -171,7 +218,11 @@ namespace Microsoft.AspNetCore.Diagnostics
                             throw new Exception("Test exception");
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             // Act
             var response = await server.CreateClient().GetAsync("/path");
@@ -241,7 +292,11 @@ namespace Microsoft.AspNetCore.Diagnostics
         {
             // Arrange
             DiagnosticListener diagnosticListener = null;
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         diagnosticListener = app.ApplicationServices.GetRequiredService<DiagnosticListener>();
@@ -251,7 +306,11 @@ namespace Microsoft.AspNetCore.Diagnostics
                             throw new CustomCompilationException(failures);
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var listener = new TestDiagnosticListener();
             diagnosticListener.SubscribeWithAdapter(listener);
 

src/Middleware/Diagnostics/test/UnitTests/ExceptionHandlerTest.cs

@@ -16,6 +16,7 @@ using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Diagnostics
@@ -28,7 +29,11 @@ namespace Microsoft.AspNetCore.Diagnostics
         [InlineData(HttpStatusCode.InternalServerError)]
         public async Task OnlyHandles_UnhandledExceptions(HttpStatusCode expectedStatusCode)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseExceptionHandler("/handle-errors");
@@ -48,8 +53,11 @@ namespace Microsoft.AspNetCore.Diagnostics
                             await context.Response.WriteAsync("An error occurred while adding a product");
                         }));
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -61,7 +69,11 @@ namespace Microsoft.AspNetCore.Diagnostics
         [Fact]
         public async Task DoesNotHandle_UnhandledExceptions_WhenResponseAlreadyStarted()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.Use(async (httpContext, next) =>
@@ -96,8 +108,11 @@ namespace Microsoft.AspNetCore.Diagnostics
                             throw new InvalidOperationException("Something bad happened");
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -110,7 +125,11 @@ namespace Microsoft.AspNetCore.Diagnostics
         public async Task ClearsResponseBuffer_BeforeRequestIsReexecuted()
         {
             var expectedResponseBody = "New response body";
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         // add response buffering
@@ -156,8 +175,11 @@ namespace Microsoft.AspNetCore.Diagnostics
                             throw new InvalidOperationException("Invalid input provided.");
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -181,7 +203,11 @@ namespace Microsoft.AspNetCore.Diagnostics
         {
             var expiresTime = DateTime.UtcNow.AddDays(5).ToString("R");
             var expectedResponseBody = "Handled error in a custom way.";
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseExceptionHandler("/handle-errors");
@@ -205,8 +231,11 @@ namespace Microsoft.AspNetCore.Diagnostics
                             throw new InvalidOperationException("Invalid input provided.");
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -230,7 +259,11 @@ namespace Microsoft.AspNetCore.Diagnostics
         {
             var expiresTime = DateTime.UtcNow.AddDays(10).ToString("R");
             var expectedResponseBody = "Hello world!";
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseExceptionHandler("/handle-errors");
@@ -253,8 +286,11 @@ namespace Microsoft.AspNetCore.Diagnostics
                             await httpContext.Response.WriteAsync(expectedResponseBody);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -280,7 +316,11 @@ namespace Microsoft.AspNetCore.Diagnostics
         public async Task DoesNotClearCacheHeaders_WhenResponseHasAlreadyStarted()
         {
             var expiresTime = DateTime.UtcNow.AddDays(10).ToString("R");
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.Use(async (httpContext, next) =>
@@ -321,8 +361,11 @@ namespace Microsoft.AspNetCore.Diagnostics
                             throw new InvalidOperationException("Something bad happened");
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -350,7 +393,11 @@ namespace Microsoft.AspNetCore.Diagnostics
             // Arrange
             DiagnosticListener diagnosticListener = null;
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         diagnosticListener = app.ApplicationServices.GetRequiredService<DiagnosticListener>();
@@ -368,7 +415,11 @@ namespace Microsoft.AspNetCore.Diagnostics
                             throw new Exception("Test exception");
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var listener = new TestDiagnosticListener();
             diagnosticListener.SubscribeWithAdapter(listener);
@@ -395,15 +446,20 @@ namespace Microsoft.AspNetCore.Diagnostics
             // Arrange
             DiagnosticListener diagnosticListener = null;
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         diagnosticListener = app.ApplicationServices.GetRequiredService<DiagnosticListener>();
                         app.UseExceptionHandler();
                     });
+                }).Build();
 
             // Act
-            var exception = Assert.Throws<InvalidOperationException>(() => new TestServer(builder));
+            var exception = Assert.Throws<InvalidOperationException>(() => host.Start());
 
             // Assert
             Assert.Equal("An error occurred when configuring the exception handler middleware. " +

src/Middleware/Diagnostics/test/UnitTests/StatusCodeMiddlewareTest.cs

@@ -10,6 +10,7 @@ using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Diagnostics
@@ -21,7 +22,11 @@ namespace Microsoft.AspNetCore.Diagnostics
         {
             var expectedStatusCode = 432;
             var destination = "/location";
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseStatusCodePagesWithRedirects("/errorPage?id={0}");
@@ -48,9 +53,13 @@ namespace Microsoft.AspNetCore.Diagnostics
                             throw new InvalidOperationException($"Invalid input provided. {context.Request.Path}");
                         });
                     });
+                }).Build();
+
+            await host.StartAsync();
+
             var expectedQueryString = $"?id={expectedStatusCode}";
             var expectedUri = $"/errorPage{expectedQueryString}";
-            using var server = new TestServer(builder);
+            using var server = host.GetTestServer();
             var client = server.CreateClient();
             var response = await client.GetAsync(destination);
             Assert.Equal(HttpStatusCode.Found, response.StatusCode);
@@ -67,7 +76,11 @@ namespace Microsoft.AspNetCore.Diagnostics
         {
             var expectedStatusCode = 432;
             var destination = "/location";
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.Use(async (context, next) =>
@@ -108,8 +121,11 @@ namespace Microsoft.AspNetCore.Diagnostics
                             throw new InvalidOperationException("Invalid input provided.");
                         });
                     });
+                }).Build();
 
-            using var server = new TestServer(builder);
+            await host.StartAsync();
+
+            using var server = host.GetTestServer();
             var client = server.CreateClient();
             var response = await client.GetAsync(destination + "?name=James");
             var content = await response.Content.ReadAsStringAsync();
@@ -121,7 +137,11 @@ namespace Microsoft.AspNetCore.Diagnostics
         {
             var expectedStatusCode = 432;
             var destination = "/location";
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseStatusCodePagesWithReExecute(pathFormat: "/errorPage", queryFormat: "?id={0}");
@@ -163,8 +183,11 @@ namespace Microsoft.AspNetCore.Diagnostics
                             throw new InvalidOperationException("Invalid input provided.");
                         });
                     });
+                }).Build();
 
-            using var server = new TestServer(builder);
+            await host.StartAsync();
+
+            using var server = host.GetTestServer();
             var client = server.CreateClient();
             var response = await client.GetAsync(destination + "?name=James");
             var content = await response.Content.ReadAsStringAsync();

src/Middleware/Diagnostics/test/testassets/DatabaseErrorPageSample/Startup.cs

@@ -4,6 +4,7 @@ using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 
 namespace DatabaseErrorPageSample
 {
@@ -26,15 +27,19 @@ namespace DatabaseErrorPageSample
             });
         }
 
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .UseKestrel()
                     .UseIISIntegration()
-                .UseStartup<Startup>()
+                    .UseStartup<Startup>();
+                })
                 .Build();
 
-            host.Run();
+            return host.RunAsync();
         }
     }
 

src/Middleware/Diagnostics/test/testassets/DeveloperExceptionPageSample/Startup.cs

@@ -8,6 +8,7 @@ using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Routing;
 using Microsoft.AspNetCore.Routing.Patterns;
+using Microsoft.Extensions.Hosting;
 
 namespace DeveloperExceptionPageSample
 {
@@ -44,15 +45,19 @@ namespace DeveloperExceptionPageSample
             });
         }
 
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .UseKestrel()
                     .UseIISIntegration()
-                .UseStartup<Startup>()
+                    .UseStartup<Startup>();
+                })
                 .Build();
 
-            host.Run();
+            return host.RunAsync();
         }
     }
 }

src/Middleware/Diagnostics/test/testassets/ExceptionHandlerSample/Startup.cs

@@ -1,10 +1,12 @@
 using System;
 using System.Text.Encodings.Web;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Diagnostics;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Features;
+using Microsoft.Extensions.Hosting;
 
 namespace ExceptionHandlerSample
 {
@@ -56,15 +58,19 @@ namespace ExceptionHandlerSample
             });
         }
 
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .UseKestrel()
                     .UseIISIntegration()
-                .UseStartup<Startup>()
+                    .UseStartup<Startup>();
+                })
                 .Build();
 
-            host.Run();
+            return host.RunAsync();
         }
     }
 }

src/Middleware/Diagnostics/test/testassets/StatusCodePagesSample/Startup.cs

@@ -11,6 +11,7 @@ using Microsoft.AspNetCore.Diagnostics;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Features;
+using Microsoft.Extensions.Hosting;
 
 namespace StatusCodePagesSample
 {
@@ -102,15 +103,18 @@ namespace StatusCodePagesSample
             });
         }
 
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .UseKestrel()
                     .UseIISIntegration()
-                .UseStartup<Startup>()
-                .Build();
+                    .UseStartup<Startup>();
+                }).Build();
 
-            host.Run();
+            return host.RunAsync();
         }
     }
 }

src/Middleware/Diagnostics/test/testassets/WelcomePageSample/Startup.cs

@@ -1,5 +1,7 @@
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
+using Microsoft.Extensions.Hosting;
 
 namespace WelcomePageSample
 {
@@ -10,15 +12,18 @@ namespace WelcomePageSample
             app.UseWelcomePage();
         }
 
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .UseKestrel()
                     .UseIISIntegration()
-                .UseStartup<Startup>()
-                .Build();
+                    .UseStartup<Startup>();
+                }).Build();
 
-            host.Run();
+            return host.RunAsync();
         }
     }
 }

src/Middleware/HeaderPropagation/test/HeaderPropagationIntegrationTest.cs

@@ -12,6 +12,7 @@ using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Xunit;
 
 namespace Microsoft.AspNetCore.HeaderPropagation.Tests
@@ -24,7 +25,11 @@ namespace Microsoft.AspNetCore.HeaderPropagation.Tests
             // Arrange
             Exception captured = null;
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddHttpClient("test").AddHeaderPropagation();
@@ -50,8 +55,11 @@ namespace Microsoft.AspNetCore.HeaderPropagation.Tests
                             }
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage();
@@ -96,10 +104,10 @@ namespace Microsoft.AspNetCore.HeaderPropagation.Tests
         {
             // Arrange
             var handler = new SimpleHandler();
-            var builder = CreateBuilder(c =>
+            using var host = await CreateHost(c =>
                 c.Headers.Add("in", "out"),
                 handler);
-            var server = new TestServer(builder);
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage();
@@ -119,13 +127,13 @@ namespace Microsoft.AspNetCore.HeaderPropagation.Tests
         {
             // Arrange
             var handler = new SimpleHandler();
-            var builder = CreateBuilder(c =>
+            using var host = await CreateHost(c =>
                 {
                     c.Headers.Add("first");
                     c.Headers.Add("second");
                 },
                 handler);
-            var server = new TestServer(builder);
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage();
@@ -144,15 +152,20 @@ namespace Microsoft.AspNetCore.HeaderPropagation.Tests
         }
 
         [Fact]
-        public void Builder_UseHeaderPropagation_Without_AddHeaderPropagation_Throws()
+        public async Task Builder_UseHeaderPropagation_Without_AddHeaderPropagation_Throws()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHeaderPropagation();
                     });
+                }).Build();
 
-            var exception = Assert.Throws<InvalidOperationException>(() => new TestServer(builder));
+            var exception = await Assert.ThrowsAsync<InvalidOperationException>(() => host.StartAsync());
             Assert.Equal(
                 "Unable to find the required services. Please add all the required services by calling 'IServiceCollection.AddHeaderPropagation' inside the call to 'ConfigureServices(...)' in the application startup code.",
                 exception.Message);
@@ -163,11 +176,11 @@ namespace Microsoft.AspNetCore.HeaderPropagation.Tests
         {
             // Arrange
             var handler = new SimpleHandler();
-            var builder = CreateBuilder(
+            using var host = await CreateHost(
                 c => c.Headers.Add("in", "out"),
                 handler,
                 c => c.Headers.Add("out", "different"));
-            var server = new TestServer(builder);
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage();
@@ -182,9 +195,13 @@ namespace Microsoft.AspNetCore.HeaderPropagation.Tests
             Assert.Equal(new[] { "test" }, handler.Headers.GetValues("different"));
         }
 
-        private IWebHostBuilder CreateBuilder(Action<HeaderPropagationOptions> configure, HttpMessageHandler primaryHandler, Action<HeaderPropagationMessageHandlerOptions> configureClient = null)
+        private async Task<IHost> CreateHost(Action<HeaderPropagationOptions> configure, HttpMessageHandler primaryHandler, Action<HeaderPropagationMessageHandlerOptions> configureClient = null)
         {
-            return new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHeaderPropagation();
@@ -208,6 +225,11 @@ namespace Microsoft.AspNetCore.HeaderPropagation.Tests
                             client.AddHeaderPropagation();
                         }
                     });
+                }).Build();
+
+            await host.StartAsync();
+
+            return host;
         }
 
         private class SimpleHandler : DelegatingHandler

src/Middleware/HealthChecks/test/UnitTests/HealthCheckEndpointRouteBuilderExtensionsTest.cs

@@ -13,6 +13,7 @@ using Moq;
 using Xunit;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Hosting;
 
 namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
 {
@@ -21,7 +22,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public void ThrowFriendlyErrorWhenServicesNotRegistered()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRouting();
@@ -34,8 +39,9 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddRouting();
                     });
+                }).Build();
 
-            var ex = Assert.Throws<InvalidOperationException>(() => new TestServer(builder));
+            var ex = Assert.Throws<InvalidOperationException>(() => host.Start());
 
             Assert.Equal(
                 "Unable to find the required services. Please add all the required services by calling " +
@@ -48,7 +54,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         public async Task MapHealthChecks_ReturnsOk()
         {
             // Arrange
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRouting();
@@ -62,7 +72,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                         services.AddRouting();
                         services.AddHealthChecks();
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             // Act
@@ -78,7 +92,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         public async Task MapHealthChecks_WithOptions_ReturnsOk()
         {
             // Arrange
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRouting();
@@ -99,7 +117,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                         services.AddRouting();
                         services.AddHealthChecks();
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             // Act

src/Middleware/HealthChecks/test/UnitTests/HealthCheckMiddlewareSampleTest.cs

@@ -1,10 +1,11 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.Net;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.TestHost;
+using Microsoft.Extensions.Hosting;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
@@ -14,10 +15,17 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task BasicStartup()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .UseStartup<HealthChecksSample.BasicStartup>();
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("/health");
@@ -29,10 +37,17 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task CustomWriterStartup()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .UseStartup<HealthChecksSample.CustomWriterStartup>();
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("/health");
@@ -45,10 +60,17 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task LivenessProbeStartup_Liveness()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .UseStartup<HealthChecksSample.LivenessProbeStartup>();
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("/health/live");
@@ -60,10 +82,17 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task LivenessProbeStartup_Readiness()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .UseStartup<HealthChecksSample.LivenessProbeStartup>();
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("/health/ready");

src/Middleware/HealthChecks/test/UnitTests/HealthCheckMiddlewareTests.cs

@@ -14,6 +14,7 @@ using Newtonsoft.Json;
 using System.Net;
 using System.Threading.Tasks;
 using Xunit;
+using Microsoft.Extensions.Hosting;
 
 namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
 {
@@ -22,13 +23,18 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public void ThrowFriendlyErrorWhenServicesNotRegistered()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health");
                     });
+                }).Build();
 
-            var ex = Assert.Throws<InvalidOperationException>(() => new TestServer(builder));
+            var ex = Assert.Throws<InvalidOperationException>(() => host.Start());
 
             Assert.Equal(
                 "Unable to find the required services. Please add all the required services by calling " +
@@ -40,7 +46,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact] // Matches based on '.Map'
         public async Task IgnoresRequestThatDoesNotMatchPath()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health");
@@ -49,7 +59,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddHealthChecks();
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("/frob");
@@ -59,7 +73,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact] // Matches based on '.Map'
         public async Task MatchIsCaseInsensitive()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health");
@@ -68,7 +86,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddHealthChecks();
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("/HEALTH");
@@ -78,7 +100,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task ReturnsPlainTextStatus()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health");
@@ -87,7 +113,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddHealthChecks();
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("/health");
@@ -100,7 +130,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task StatusCodeIs200IfNoChecks()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health");
@@ -109,7 +143,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddHealthChecks();
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("/health");
@@ -122,7 +160,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task StatusCodeIs200IfAllChecksHealthy()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health");
@@ -134,7 +176,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                             .AddCheck("Bar", () => HealthCheckResult.Healthy("A-ok!"))
                             .AddCheck("Baz", () => HealthCheckResult.Healthy("A-ok!"));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("/health");
@@ -147,7 +193,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task StatusCodeIs200IfCheckIsDegraded()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health");
@@ -159,7 +209,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                             .AddCheck("Bar", () => HealthCheckResult.Degraded("Not so great."))
                             .AddCheck("Baz", () => HealthCheckResult.Healthy("A-ok!"));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("/health");
@@ -172,7 +226,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task StatusCodeIs503IfCheckIsUnhealthy()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health");
@@ -184,7 +242,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                             .AddAsyncCheck("Bar", () => Task.FromResult(HealthCheckResult.Unhealthy("Pretty bad.")))
                             .AddAsyncCheck("Baz", () => Task.FromResult(HealthCheckResult.Healthy("A-ok!")));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("/health");
@@ -197,7 +259,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task StatusCodeIs503IfCheckHasUnhandledException()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health");
@@ -209,7 +275,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                             .AddAsyncCheck("Bar", () => throw null)
                             .AddAsyncCheck("Baz", () => Task.FromResult(HealthCheckResult.Healthy("A-ok!")));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("/health");
@@ -227,7 +297,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                 status = "Unhealthy",
             });
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health", new HealthCheckOptions()
@@ -247,7 +321,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                             .AddAsyncCheck("Bar", () => Task.FromResult(HealthCheckResult.Unhealthy("Pretty bad.")))
                             .AddAsyncCheck("Baz", () => Task.FromResult(HealthCheckResult.Healthy("A-ok!")));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("/health");
@@ -261,7 +339,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task NoResponseWriterReturnsEmptyBody()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health", new HealthCheckOptions()
@@ -276,7 +358,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                             .AddAsyncCheck("Bar", () => Task.FromResult(HealthCheckResult.Unhealthy("Pretty bad.")))
                             .AddAsyncCheck("Baz", () => Task.FromResult(HealthCheckResult.Healthy("A-ok!")));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("/health");
@@ -288,7 +374,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task CanSetCustomStatusCodes()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health", new HealthCheckOptions()
@@ -303,7 +393,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddHealthChecks();
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("/health");
@@ -315,7 +409,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task SetsCacheHeaders()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health");
@@ -324,7 +422,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddHealthChecks();
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("/health");
@@ -339,7 +441,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task CanSuppressCacheHeaders()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health", new HealthCheckOptions()
@@ -351,7 +457,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddHealthChecks();
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("/health");
@@ -366,7 +476,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task CanFilterChecks()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health", new HealthCheckOptions()
@@ -382,7 +496,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                             .AddAsyncCheck("Bar", () => Task.FromResult(HealthCheckResult.Unhealthy("A-ok!")))
                             .AddAsyncCheck("Baz", () => Task.FromResult(HealthCheckResult.Healthy("A-ok!")));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("/health");
@@ -395,7 +513,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task CanListenWithoutPath_AcceptsRequest()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks(default);
@@ -404,8 +526,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddHealthChecks();
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("http://localhost:5001/health");
@@ -418,7 +543,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task CanListenWithPath_AcceptsRequestWithExtraSlash()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health");
@@ -427,8 +556,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddHealthChecks();
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("http://localhost:5001/health/");
@@ -439,7 +571,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task CanListenWithPath_AcceptsRequestWithCaseInsensitiveMatch()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health");
@@ -448,8 +584,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddHealthChecks();
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("http://localhost:5001/HEALTH");
@@ -462,7 +601,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task CanListenWithPath_RejectsRequestWithExtraSegments()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health");
@@ -471,8 +614,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddHealthChecks();
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("http://localhost:5001/health/detailed");
@@ -484,7 +630,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task CanListenWithPath_MultipleMiddleware_LeastSpecificFirst()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         // Throws if used
@@ -499,8 +649,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddHealthChecks();
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("http://localhost:5001/health/detailed");
@@ -514,7 +667,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task CanListenWithPath_MultipleMiddleware_MostSpecificFirst()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHealthChecks("/health/detailed");
@@ -529,8 +686,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddHealthChecks();
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("http://localhost:5001/health/detailed");
@@ -543,7 +703,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task CanListenOnPort_AcceptsRequest_OnSpecifiedPort()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.Use(next => async (context) =>
@@ -560,8 +724,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddHealthChecks();
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("http://localhost:5001/health");
@@ -574,7 +741,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task CanListenOnPortWithoutPath_AcceptsRequest_OnSpecifiedPort()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.Use(next => async (context) =>
@@ -591,8 +762,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddHealthChecks();
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("http://localhost:5001/health");
@@ -605,7 +779,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task CanListenOnPort_RejectsRequest_OnOtherPort()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.Use(next => async (context) =>
@@ -622,8 +800,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddHealthChecks();
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("http://localhost:5000/health");
@@ -634,7 +815,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task CanListenOnPort_MultipleMiddleware()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.Use(next => async (context) =>
@@ -657,8 +842,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddHealthChecks();
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("http://localhost:5001/health/detailed");
@@ -671,7 +859,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
         [Fact]
         public async Task CanListenOnPort_MultipleMiddleware_DifferentPorts()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.Use(next => async (context) =>
@@ -694,8 +886,11 @@ namespace Microsoft.AspNetCore.Diagnostics.HealthChecks
                     {
                         services.AddHealthChecks();
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var response = await client.GetAsync("http://localhost:5001/health");

src/Middleware/HealthChecks/test/testassets/HealthChecksSample/Program.cs

@@ -1,8 +1,10 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 
 namespace HealthChecksSample
@@ -25,12 +27,12 @@ namespace HealthChecksSample
             };
         }
 
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            BuildWebHost(args).Run();
+            return BuildWebHost(args).RunAsync();
         }
 
-        public static IWebHost BuildWebHost(string[] args)
+        public static IHost BuildWebHost(string[] args)
         {
             var config = new ConfigurationBuilder()
                 .SetBasePath(Directory.GetCurrentDirectory())
@@ -45,7 +47,10 @@ namespace HealthChecksSample
                 startupType = typeof(BasicStartup);
             }
 
-            return new WebHostBuilder()
+            return new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .UseConfiguration(config)
                     .ConfigureLogging(builder =>
                     {
@@ -54,7 +59,8 @@ namespace HealthChecksSample
                         builder.AddConsole();
                     })
                     .UseKestrel()
-                .UseStartup(startupType)
+                    .UseStartup(startupType);
+                })
                 .Build();
         }
 

src/Middleware/HostFiltering/sample/Program.cs

@@ -1,22 +1,27 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 
 namespace HostFilteringSample
 {
     public class Program
     {
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            BuildWebHost(args).Run();
+            return BuildWebHost(args).RunAsync();
         }
 
-        public static IWebHost BuildWebHost(string[] args)
+        public static IHost BuildWebHost(string[] args)
         {
-            var hostBuilder = new WebHostBuilder()
+            var hostBuilder = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .ConfigureLogging((_, factory) =>
                     {
                         factory.SetMinimumLevel(LogLevel.Debug);
@@ -30,6 +35,7 @@ namespace HostFilteringSample
                     })
                     .UseKestrel()
                     .UseStartup<Startup>();
+                });
 
             return hostBuilder.Build();
         }

src/Middleware/HostFiltering/test/HostFilteringMiddlewareTests.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
@@ -9,6 +9,7 @@ using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Options;
 using Microsoft.Extensions.Primitives;
 using Microsoft.Net.Http.Headers;
@@ -21,12 +22,20 @@ namespace Microsoft.AspNetCore.HostFiltering
         [Fact]
         public async Task MissingConfigThrows()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHostFiltering();
                     });
-            await Assert.ThrowsAsync<InvalidOperationException>(() => new TestServer(builder).SendAsync(_ => { }));
+                }).Build();
+
+            await host.StartAsync();
+
+            await Assert.ThrowsAsync<InvalidOperationException>(() => host.GetTestServer().SendAsync(_ => { }));
         }
 
         [Theory]
@@ -34,7 +43,11 @@ namespace Microsoft.AspNetCore.HostFiltering
         [InlineData(false, 400)]
         public async Task AllowsMissingHost(bool allowed, int status)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddHostFiltering(options =>
@@ -57,7 +70,11 @@ namespace Microsoft.AspNetCore.HostFiltering
                             return Task.CompletedTask;
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var response = await server.CreateClient().GetAsync("/");
             Assert.Equal(status, (int)response.StatusCode);
         }
@@ -67,7 +84,11 @@ namespace Microsoft.AspNetCore.HostFiltering
         [InlineData(false, 400)]
         public async Task AllowsEmptyHost(bool allowed, int status)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddHostFiltering(options =>
@@ -92,7 +113,11 @@ namespace Microsoft.AspNetCore.HostFiltering
                         });
                         app.Run(c => Task.CompletedTask);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var response = await server.CreateClient().GetAsync("/");
             Assert.Equal(status, (int)response.StatusCode);
         }
@@ -113,9 +138,13 @@ namespace Microsoft.AspNetCore.HostFiltering
         [InlineData("xn--c1yn36f:443", "點看")]
         [InlineData("[::ABC]", "[::aBc]")]
         [InlineData("[::1]:80", "[::1]")]
-        public async Task AllowsSpecifiedHost(string host, string allowedHost)
+        public async Task AllowsSpecifiedHost(string hosturl, string allowedHost)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddHostFiltering(options =>
@@ -129,13 +158,17 @@ namespace Microsoft.AspNetCore.HostFiltering
                         {
                             // TestHost's ClientHandler doesn't let you set the host header, only the host in the URI
                             // and that would over-normalize some of our test conditions like casing.
-                        ctx.Request.Headers[HeaderNames.Host] = host;
+                            ctx.Request.Headers[HeaderNames.Host] = hosturl;
                             return next();
                         });
                         app.UseHostFiltering();
                         app.Run(c => Task.CompletedTask);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var response = await server.CreateRequest("/").GetAsync();
             Assert.Equal(200, (int)response.StatusCode);
         }
@@ -157,9 +190,13 @@ namespace Microsoft.AspNetCore.HostFiltering
         [InlineData("點看", "點看")]
         [InlineData("[::1", "[::1]")]
         [InlineData("[::1:80", "[::1]")]
-        public async Task RejectsMismatchedHosts(string host, string allowedHost)
+        public async Task RejectsMismatchedHosts(string hosturl, string allowedHost)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddHostFiltering(options =>
@@ -173,13 +210,17 @@ namespace Microsoft.AspNetCore.HostFiltering
                         {
                             // TestHost's ClientHandler doesn't let you set the host header, only the host in the URI
                             // and that would reject some of our test conditions.
-                        ctx.Request.Headers[HeaderNames.Host] = host;
+                            ctx.Request.Headers[HeaderNames.Host] = hosturl;
                             return next();
                         });
                         app.UseHostFiltering();
                         app.Run(c => throw new NotImplementedException("App"));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var response = await server.CreateRequest("/").GetAsync();
             Assert.Equal(400, (int)response.StatusCode);
         }
@@ -191,7 +232,11 @@ namespace Microsoft.AspNetCore.HostFiltering
             config["AllowedHosts"] = "localhost";
             var currentHost = "otherHost";
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddHostFiltering(options =>
@@ -210,7 +255,11 @@ namespace Microsoft.AspNetCore.HostFiltering
                         app.UseHostFiltering();
                         app.Run(c => Task.CompletedTask);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var response = await server.CreateRequest("/").GetAsync();
             Assert.Equal(400, (int)response.StatusCode);
 

src/Middleware/HttpOverrides/sample/Startup.cs

@@ -1,7 +1,9 @@
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.HttpOverrides;
+using Microsoft.Extensions.Hosting;
 
 namespace HttpOverridesSample
 {
@@ -30,15 +32,19 @@ namespace HttpOverridesSample
         }
 
         // Entry point for the application.
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .UseKestrel()
                     // .UseIIS() // This repo can no longer reference IIS because IISIntegration depends on it.
-                .UseStartup<Startup>()
+                    .UseStartup<Startup>();
+                })
                 .Build();
 
-            host.Run();
+            return host.RunAsync();
         }
     }
 }

src/Middleware/HttpOverrides/test/CertificateForwardingTest.cs

@@ -11,6 +11,7 @@ using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Options;
 using Microsoft.Net.Http.Headers;
 using Xunit;
@@ -42,7 +43,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [Fact]
         public async Task VerifyHeaderIsUsedIfNoCertificateAlreadySet()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddCertificateForwarding(options => { });
@@ -61,7 +66,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             await next();
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -72,7 +81,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [Fact]
         public async Task VerifyHeaderOverridesCertificateEvenAlreadySet()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddCertificateForwarding(options => { });
@@ -92,7 +105,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             await next();
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -103,7 +120,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [Fact]
         public async Task VerifySettingTheAzureHeaderOnTheForwarderOptionsWorks()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddCertificateForwarding(options => options.CertificateHeader = "X-ARR-ClientCert");
@@ -122,7 +143,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             await next();
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -133,7 +158,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [Fact]
         public async Task VerifyACustomHeaderFailsIfTheHeaderIsNotPresent()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddCertificateForwarding(options => options.CertificateHeader = "some-random-header");
@@ -152,7 +181,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             await next();
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -163,7 +196,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [Fact]
         public async Task VerifyArrHeaderEncodedCertFailsOnBadEncoding()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddCertificateForwarding(options => { });
@@ -182,7 +219,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             await next();
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {

src/Middleware/HttpOverrides/test/ForwardedHeadersMiddlewareTest.cs

@@ -9,6 +9,7 @@ using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Net.Http.Headers;
 using Xunit;
 
@@ -19,7 +20,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [Fact]
         public async Task XForwardedForDefaultSettingsChangeRemoteIpAndPort()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(new ForwardedHeadersOptions
@@ -27,7 +32,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             ForwardedHeaders = ForwardedHeaders.XForwardedFor
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -46,7 +55,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [InlineData(1, "11.111.111.11.12345", "10.0.0.1", 99)] // Invalid
         public async Task XForwardedForFirstValueIsInvalid(int limit, string header, string expectedIp, int expectedPort)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(new ForwardedHeadersOptions
@@ -55,7 +68,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             ForwardLimit = limit,
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -92,7 +109,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [InlineData(3, "13.113.113.13:34567, 12.112.112.12:23456, 11.111.111.11:12345", "13.113.113.13", 34567, "", true)]
         public async Task XForwardedForForwardLimit(int limit, string header, string expectedIp, int expectedPort, string remainingHeader, bool requireSymmetry)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         var options = new ForwardedHeadersOptions
@@ -105,7 +126,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                         options.KnownNetworks.Clear();
                         app.UseForwardedHeaders(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -127,7 +152,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [InlineData("::", false)]
         public async Task XForwardedForLoopback(string originalIp, bool expectForwarded)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(new ForwardedHeadersOptions
@@ -135,7 +164,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             ForwardedHeaders = ForwardedHeaders.XForwardedFor,
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -185,7 +218,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [InlineData(3, "13.113.113.13;34567, 12.112.112.12:23456, 11.111.111.11:12345", "10.0.0.1,11.111.111.11,12.112.112.12", "12.112.112.12", 23456, true)] // Invalid 3rd IP
         public async Task XForwardedForForwardKnownIps(int limit, string header, string knownIPs, string expectedIp, int expectedPort, bool requireSymmetry)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         var options = new ForwardedHeadersOptions
@@ -200,7 +237,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                         }
                         app.UseForwardedHeaders(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -216,7 +257,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [Fact]
         public async Task XForwardedForOverrideBadIpDoesntChangeRemoteIp()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(new ForwardedHeadersOptions
@@ -224,7 +269,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             ForwardedHeaders = ForwardedHeaders.XForwardedFor
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -237,7 +286,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [Fact]
         public async Task XForwardedHostOverrideChangesRequestHost()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(new ForwardedHeadersOptions
@@ -245,7 +298,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             ForwardedHeaders = ForwardedHeaders.XForwardedHost
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -291,11 +348,15 @@ namespace Microsoft.AspNetCore.HttpOverrides
 
         [Theory]
         [MemberData(nameof(HostHeaderData))]
-        public async Task XForwardedHostAllowsValidCharacters(string host)
+        public async Task XForwardedHostAllowsValidCharacters(string hostHeader)
         {
             var assertsExecuted = false;
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(new ForwardedHeadersOptions
@@ -304,16 +365,20 @@ namespace Microsoft.AspNetCore.HttpOverrides
                         });
                         app.Run(context =>
                         {
-                        Assert.Equal(host, context.Request.Host.ToString());
+                            Assert.Equal(hostHeader, context.Request.Host.ToString());
                             assertsExecuted = true;
                             return Task.FromResult(0);
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             await server.SendAsync(c =>
             {
-                c.Request.Headers["X-Forwarded-Host"] = host;
+                c.Request.Headers["X-Forwarded-Host"] = hostHeader;
             });
             Assert.True(assertsExecuted);
         }
@@ -368,11 +433,15 @@ namespace Microsoft.AspNetCore.HttpOverrides
 
         [Theory]
         [MemberData(nameof(HostHeaderInvalidData))]
-        public async Task XForwardedHostFailsForInvalidCharacters(string host)
+        public async Task XForwardedHostFailsForInvalidCharacters(string hostHeader)
         {
             var assertsExecuted = false;
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(new ForwardedHeadersOptions
@@ -381,16 +450,20 @@ namespace Microsoft.AspNetCore.HttpOverrides
                         });
                         app.Run(context =>
                         {
-                        Assert.NotEqual(host, context.Request.Host.Value);
+                            Assert.NotEqual(hostHeader, context.Request.Host.Value);
                             assertsExecuted = true;
                             return Task.FromResult(0);
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             await server.SendAsync(c =>
             {
-                c.Request.Headers["X-Forwarded-Host"] = host;
+                c.Request.Headers["X-Forwarded-Host"] = hostHeader;
             });
             Assert.True(assertsExecuted);
         }
@@ -411,10 +484,14 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [InlineData("xn--c1yn36f:443", "點看")]
         [InlineData("[::ABC]", "[::aBc]")]
         [InlineData("[::1]:80", "[::1]")]
-        public async Task XForwardedHostAllowsSpecifiedHost(string host, string allowedHost)
+        public async Task XForwardedHostAllowsSpecifiedHost(string hostHeader, string allowedHost)
         {
             bool assertsExecuted = false;
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(new ForwardedHeadersOptions
@@ -424,15 +501,19 @@ namespace Microsoft.AspNetCore.HttpOverrides
                         });
                         app.Run(context =>
                         {
-                        Assert.Equal(host, context.Request.Headers[HeaderNames.Host]);
+                            Assert.Equal(hostHeader, context.Request.Headers[HeaderNames.Host]);
                             assertsExecuted = true;
                             return Task.FromResult(0);
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var response = await server.SendAsync(ctx =>
             {
-                ctx.Request.Headers["X-forwarded-Host"] = host;
+                ctx.Request.Headers["X-forwarded-Host"] = hostHeader;
             });
             Assert.True(assertsExecuted);
         }
@@ -454,10 +535,14 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [InlineData("點看", "點看")]
         [InlineData("[::1", "[::1]")]
         [InlineData("[::1:80", "[::1]")]
-        public async Task XForwardedHostFailsMismatchedHosts(string host, string allowedHost)
+        public async Task XForwardedHostFailsMismatchedHosts(string hostHeader, string allowedHost)
         {
             bool assertsExecuted = false;
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(new ForwardedHeadersOptions
@@ -467,15 +552,19 @@ namespace Microsoft.AspNetCore.HttpOverrides
                         });
                         app.Run(context =>
                         {
-                        Assert.NotEqual<string>(host, context.Request.Headers[HeaderNames.Host]);
+                            Assert.NotEqual<string>(hostHeader, context.Request.Headers[HeaderNames.Host]);
                             assertsExecuted = true;
                             return Task.FromResult(0);
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var response = await server.SendAsync(ctx =>
             {
-                ctx.Request.Headers["X-forwarded-Host"] = host;
+                ctx.Request.Headers["X-forwarded-Host"] = hostHeader;
             });
             Assert.True(assertsExecuted);
         }
@@ -484,7 +573,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         public async Task XForwardedHostStopsAtFirstUnspecifiedHost()
         {
             bool assertsExecuted = false;
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(new ForwardedHeadersOptions
@@ -500,7 +593,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             return Task.FromResult(0);
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var response = await server.SendAsync(ctx =>
             {
                 ctx.Request.Headers["X-forwarded-Host"] = "stuff:523, bar.foo.com:432, bar.com:80";
@@ -518,7 +615,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [InlineData(10, "h3, h2, h1", "h3")]
         public async Task XForwardedProtoOverrideChangesRequestProtocol(int limit, string header, string expected)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(new ForwardedHeadersOptions
@@ -527,7 +628,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             ForwardLimit = limit,
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -559,7 +664,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         {
             var assertsExecuted = false;
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(new ForwardedHeadersOptions
@@ -573,7 +682,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             return Task.FromResult(0);
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             await server.SendAsync(c =>
             {
@@ -608,7 +721,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         {
             var assertsExecuted = false;
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(new ForwardedHeadersOptions
@@ -622,7 +739,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             return Task.FromResult(0);
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             await server.SendAsync(c =>
             {
@@ -642,7 +763,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [InlineData(10, "h3, h2, h1", "::1, badip, ::1", "h1")]
         public async Task XForwardedProtoOverrideLimitedByXForwardedForCount(int limit, string protoHeader, string forHeader, string expected)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(new ForwardedHeadersOptions
@@ -652,7 +777,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             ForwardLimit = limit,
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -676,7 +805,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [InlineData(10, "h3, h2, h1", "::1, badip, ::1", "h1")]
         public async Task XForwardedProtoOverrideCanBeIndependentOfXForwardedForCount(int limit, string protoHeader, string forHeader, string expected)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(new ForwardedHeadersOptions
@@ -686,7 +819,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             ForwardLimit = limit,
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -712,7 +849,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [InlineData("h2, h1", "E::, D::", "F::", true, "http")]
         public async Task XForwardedProtoOverrideLimitedByLoopback(string protoHeader, string forHeader, string remoteIp, bool loopback, string expected)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         var options = new ForwardedHeadersOptions
@@ -728,7 +869,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                         }
                         app.UseForwardedHeaders(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -753,7 +898,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [Fact]
         public async Task AllForwardsEnabledChangeRequestRemoteIpHostandProtocol()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(new ForwardedHeadersOptions
@@ -761,7 +910,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             ForwardedHeaders = ForwardedHeaders.All
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -778,7 +931,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [Fact]
         public async Task AllOptionsDisabledRequestDoesntChange()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(new ForwardedHeadersOptions
@@ -786,7 +943,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             ForwardedHeaders = ForwardedHeaders.None
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -803,7 +964,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [Fact]
         public async Task PartiallyEnabledForwardsPartiallyChangesRequest()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(new ForwardedHeadersOptions
@@ -811,7 +976,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             ForwardedHeaders = ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -852,12 +1021,20 @@ namespace Microsoft.AspNetCore.HttpOverrides
                 options.KnownNetworks.Add(new IPNetwork(networkIp, prefixLength));
             }
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseForwardedHeaders(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -872,7 +1049,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [InlineData(2, "httpa, httpb, httpc", "httpb", "httpa")]
         public async Task ForwardersWithDIOptionsRunsOnce(int limit, string header, string expectedScheme, string remainingHeader)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.Configure<ForwardedHeadersOptions>(options =>
@@ -888,7 +1069,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                         app.UseForwardedHeaders();
                         app.UseForwardedHeaders();
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {
@@ -904,7 +1089,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         [InlineData(2, "httpa, httpb, httpc", "httpa", "")]
         public async Task ForwardersWithDirectOptionsRunsTwice(int limit, string header, string expectedScheme, string remainingHeader)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         var options = new ForwardedHeadersOptions
@@ -917,7 +1106,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                         app.UseForwardedHeaders(options);
                         app.UseForwardedHeaders(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var context = await server.SendAsync(c =>
             {

src/Middleware/HttpOverrides/test/HttpMethodOverrideMiddlewareTest.cs

@@ -7,6 +7,7 @@ using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.TestHost;
+using Microsoft.Extensions.Hosting;
 using Xunit;
 
 namespace Microsoft.AspNetCore.HttpOverrides
@@ -17,7 +18,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         public async Task XHttpMethodOverrideHeaderAvaiableChangesRequestMethod()
         {
             var assertsExecuted = false;
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHttpMethodOverride();
@@ -28,7 +33,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             return Task.FromResult(0);
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var req = new HttpRequestMessage(HttpMethod.Post, "");
             req.Headers.Add("X-Http-Method-Override", "DELETE");
@@ -40,18 +49,26 @@ namespace Microsoft.AspNetCore.HttpOverrides
         public async Task XHttpMethodOverrideHeaderUnavaiableDoesntChangeRequestMethod()
         {
             var assertsExecuted = false;
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHttpMethodOverride();
                         app.Run(context =>
                         {
-                        Assert.Equal("POST",context.Request.Method);
+                            Assert.Equal("POST", context.Request.Method);
                             assertsExecuted = true;
                             return Task.FromResult(0);
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var req = new HttpRequestMessage(HttpMethod.Post, "");
             await server.CreateClient().SendAsync(req);
@@ -62,7 +79,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         public async Task XHttpMethodOverrideFromGetRequestDoesntChangeMethodType()
         {
             var assertsExecuted = false;
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHttpMethodOverride();
@@ -73,7 +94,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             return Task.FromResult(0);
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var req = new HttpRequestMessage(HttpMethod.Get, "");
             await server.CreateClient().SendAsync(req);
@@ -85,7 +110,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         public async Task FormFieldAvailableChangesRequestMethod()
         {
             var assertsExecuted = false;
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHttpMethodOverride(new HttpMethodOverrideOptions()
@@ -99,7 +128,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             return Task.FromResult(0);
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var req = new HttpRequestMessage(HttpMethod.Post, "");
             req.Content = new FormUrlEncodedContent(new Dictionary<string, string>()
@@ -116,7 +149,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         public async Task FormFieldUnavailableDoesNotChangeRequestMethod()
         {
             var assertsExecuted = false;
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHttpMethodOverride(new HttpMethodOverrideOptions()
@@ -130,7 +167,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             return Task.FromResult(0);
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var req = new HttpRequestMessage(HttpMethod.Post, "");
             req.Content = new FormUrlEncodedContent(new Dictionary<string, string>()
@@ -146,7 +187,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
         public async Task FormFieldEmptyDoesNotChangeRequestMethod()
         {
             var assertsExecuted = false;
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseHttpMethodOverride(new HttpMethodOverrideOptions()
@@ -160,7 +205,11 @@ namespace Microsoft.AspNetCore.HttpOverrides
                             return Task.FromResult(0);
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var req = new HttpRequestMessage(HttpMethod.Post, "");
             req.Content = new FormUrlEncodedContent(new Dictionary<string, string>()

src/Middleware/HttpsPolicy/sample/Startup.cs

@@ -49,9 +49,12 @@ namespace HttpsSample
         }
 
         // Entry point for the application.
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .UseKestrel(
                     options =>
                     {
@@ -69,10 +72,11 @@ namespace HttpsSample
                         factory.SetMinimumLevel(LogLevel.Debug);
                         factory.AddConsole();
                     })
-                .UseStartup<Startup>()
+                    .UseStartup<Startup>();
+                })
                 .Build();
 
-            host.Run();
+            return host.RunAsync();
         }
     }
 }

src/Middleware/HttpsPolicy/test/HstsMiddlewareTests.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
@@ -12,6 +12,7 @@ using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Logging.Testing;
 using Microsoft.Net.Http.Headers;
@@ -24,7 +25,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
         [Fact]
         public async Task SetOptionsWithDefault_SetsMaxAgeToCorrectValue()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                     })
@@ -36,8 +41,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                             return context.Response.WriteAsync("Hello world");
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
             client.BaseAddress = new Uri("https://example.com:5050");
 
@@ -58,10 +66,15 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
         [InlineData(50000, true, true, "max-age=50000; includeSubDomains; preload")]
         public async Task SetOptionsThroughConfigure_SetsHeaderCorrectly(int maxAge, bool includeSubDomains, bool preload, string expected)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
-                    services.Configure<HstsOptions>(options => {
+                        services.Configure<HstsOptions>(options =>
+                        {
                             options.Preload = preload;
                             options.IncludeSubDomains = includeSubDomains;
                             options.MaxAge = TimeSpan.FromSeconds(maxAge);
@@ -75,8 +88,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                             return context.Response.WriteAsync("Hello world");
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
             client.BaseAddress = new Uri("https://example.com:5050");
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -96,10 +112,15 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
         [InlineData(50000, true, true, "max-age=50000; includeSubDomains; preload")]
         public async Task SetOptionsThroughHelper_SetsHeaderCorrectly(int maxAge, bool includeSubDomains, bool preload, string expected)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
-                    services.AddHsts(options => {
+                        services.AddHsts(options =>
+                        {
                             options.Preload = preload;
                             options.IncludeSubDomains = includeSubDomains;
                             options.MaxAge = TimeSpan.FromSeconds(maxAge);
@@ -113,8 +134,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                             return context.Response.WriteAsync("Hello world");
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
             client.BaseAddress = new Uri("https://example.com:5050");
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -131,14 +155,18 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
         [InlineData("LOCALHOST")]
         [InlineData("127.0.0.1")]
         [InlineData("[::1]")]
-        public async Task DefaultExcludesCommonLocalhostDomains_DoesNotSetHstsHeader(string host)
+        public async Task DefaultExcludesCommonLocalhostDomains_DoesNotSetHstsHeader(string hostUrl)
         {
             var sink = new TestSink(
                 TestSink.EnableWithTypeName<HstsMiddleware>,
                 TestSink.EnableWithTypeName<HstsMiddleware>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<ILoggerFactory>(loggerFactory);
@@ -151,9 +179,13 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                             return context.Response.WriteAsync("Hello world");
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
-            client.BaseAddress = new Uri($"https://{host}:5050");
+            client.BaseAddress = new Uri($"https://{hostUrl}:5050");
             var request = new HttpRequestMessage(HttpMethod.Get, "");
 
             var response = await client.SendAsync(request);
@@ -166,21 +198,25 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
             Assert.Single(logMessages);
             var message = logMessages.Single();
             Assert.Equal(LogLevel.Debug, message.LogLevel);
-            Assert.Equal($"The host '{host}' is excluded. Skipping HSTS header.", message.State.ToString(), ignoreCase: true);
+            Assert.Equal($"The host '{hostUrl}' is excluded. Skipping HSTS header.", message.State.ToString(), ignoreCase: true);
         }
 
         [Theory]
         [InlineData("localhost")]
         [InlineData("127.0.0.1")]
         [InlineData("[::1]")]
-        public async Task AllowLocalhostDomainsIfListIsReset_SetHstsHeader(string host)
+        public async Task AllowLocalhostDomainsIfListIsReset_SetHstsHeader(string hostUrl)
         {
             var sink = new TestSink(
                 TestSink.EnableWithTypeName<HstsMiddleware>,
                 TestSink.EnableWithTypeName<HstsMiddleware>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<ILoggerFactory>(loggerFactory);
@@ -198,9 +234,13 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                             return context.Response.WriteAsync("Hello world");
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
-            client.BaseAddress = new Uri($"https://{host}:5050");
+            client.BaseAddress = new Uri($"https://{hostUrl}:5050");
             var request = new HttpRequestMessage(HttpMethod.Get, "");
 
             var response = await client.SendAsync(request);
@@ -220,20 +260,25 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
         [InlineData("example.com")]
         [InlineData("Example.com")]
         [InlineData("EXAMPLE.COM")]
-        public async Task AddExcludedDomains_DoesNotAddHstsHeader(string host)
+        public async Task AddExcludedDomains_DoesNotAddHstsHeader(string hostUrl)
         {
             var sink = new TestSink(
                 TestSink.EnableWithTypeName<HstsMiddleware>,
                 TestSink.EnableWithTypeName<HstsMiddleware>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<ILoggerFactory>(loggerFactory);
 
-                    services.AddHsts(options => {
-                        options.ExcludedHosts.Add(host);
+                        services.AddHsts(options =>
+                        {
+                            options.ExcludedHosts.Add(hostUrl);
                         });
                     })
                     .Configure(app =>
@@ -244,9 +289,13 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                             return context.Response.WriteAsync("Hello world");
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
-            client.BaseAddress = new Uri($"https://{host}:5050");
+            client.BaseAddress = new Uri($"https://{hostUrl}:5050");
             var request = new HttpRequestMessage(HttpMethod.Get, "");
 
             var response = await client.SendAsync(request);
@@ -259,7 +308,7 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
             Assert.Single(logMessages);
             var message = logMessages.Single();
             Assert.Equal(LogLevel.Debug, message.LogLevel);
-            Assert.Equal($"The host '{host}' is excluded. Skipping HSTS header.", message.State.ToString(), ignoreCase: true);
+            Assert.Equal($"The host '{hostUrl}' is excluded. Skipping HSTS header.", message.State.ToString(), ignoreCase: true);
         }
 
         [Fact]
@@ -270,7 +319,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                 TestSink.EnableWithTypeName<HstsMiddleware>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<ILoggerFactory>(loggerFactory);
@@ -283,7 +336,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                             return context.Response.WriteAsync("Hello world");
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
             client.BaseAddress = new Uri("http://example.com:5050");
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -309,7 +366,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                 TestSink.EnableWithTypeName<HstsMiddleware>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<ILoggerFactory>(loggerFactory);
@@ -322,7 +383,10 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                             return context.Response.WriteAsync("Hello world");
                         });
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+            var server = host.GetTestServer();
             var client = server.CreateClient();
             client.BaseAddress = new Uri("https://example.com:5050");
             var request = new HttpRequestMessage(HttpMethod.Get, "");

src/Middleware/HttpsPolicy/test/HttpsPolicyTests.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
@@ -13,6 +13,7 @@ using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Net.Http.Headers;
 using Xunit;
 
@@ -30,8 +31,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
         [InlineData(302, 5050, 2592000, true, true, "max-age=2592000; includeSubDomains; preload", "https://localhost:5050/")]
         public async Task SetsBothHstsAndHttpsRedirection_RedirectOnFirstRequest_HstsOnSecondRequest(int statusCode, int? tlsPort, int maxAge, bool includeSubDomains, bool preload, string expectedHstsHeader, string expectedUrl)
         {
-
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.Configure<HttpsRedirectionOptions>(options =>
@@ -56,10 +60,12 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                             return context.Response.WriteAsync("Hello world");
                         });
                     });
+                }).Build();
 
-            var featureCollection = new FeatureCollection();
-            featureCollection.Set<IServerAddressesFeature>(new ServerAddressesFeature());
-            var server = new TestServer(builder, featureCollection);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
+            server.Features.Set<IServerAddressesFeature>(new ServerAddressesFeature());
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");

src/Middleware/HttpsPolicy/test/HttpsRedirectionMiddlewareTests.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
@@ -8,11 +8,13 @@ using System.Net.Http;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Hosting.Server;
 using Microsoft.AspNetCore.Hosting.Server.Features;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Logging.Testing;
 using Xunit;
@@ -28,7 +30,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                 TestSink.EnableWithTypeName<HttpsRedirectionMiddleware>,
                 TestSink.EnableWithTypeName<HttpsRedirectionMiddleware>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<ILoggerFactory>(loggerFactory);
@@ -41,8 +47,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                             return context.Response.WriteAsync("Hello world");
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -71,7 +80,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                 TestSink.EnableWithTypeName<HttpsRedirectionMiddleware>,
                 TestSink.EnableWithTypeName<HttpsRedirectionMiddleware>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<ILoggerFactory>(loggerFactory);
@@ -89,8 +102,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                             return context.Response.WriteAsync("Hello world");
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -120,7 +136,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                 TestSink.EnableWithTypeName<HttpsRedirectionMiddleware>,
                 TestSink.EnableWithTypeName<HttpsRedirectionMiddleware>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<ILoggerFactory>(loggerFactory);
@@ -138,8 +158,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                             return context.Response.WriteAsync("Hello world");
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -169,7 +192,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
         public async Task SetHttpsPortEnvironmentVariableAndServerFeature_ReturnsCorrectStatusCodeOnResponse(
             int? optionsHttpsPort, string configHttpsPort, string serverAddressFeatureUrl, string expectedUrl)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddHttpsRedirection(options =>
@@ -186,17 +213,18 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                         });
                     });
 
-            builder.UseSetting("HTTPS_PORT", configHttpsPort);
+                    webHostBuilder.UseSetting("HTTPS_PORT", configHttpsPort);
+                }).Build();
 
-            var featureCollection = new FeatureCollection();
-            featureCollection.Set<IServerAddressesFeature>(new ServerAddressesFeature());
-
-            var server = new TestServer(builder, featureCollection);
+            var server = host.GetTestServer();
+            server.Features.Set<IServerAddressesFeature>(new ServerAddressesFeature());
             if (serverAddressFeatureUrl != null)
             {
                 server.Features.Get<IServerAddressesFeature>().Addresses.Add(serverAddressFeatureUrl);
             }
 
+            await host.StartAsync();
+
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -213,7 +241,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                 TestSink.EnableWithTypeName<HttpsRedirectionMiddleware>,
                 TestSink.EnableWithTypeName<HttpsRedirectionMiddleware>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<ILoggerFactory>(loggerFactory);
@@ -226,12 +258,13 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                            return context.Response.WriteAsync("Hello world");
                        });
                    });
+                }).Build();
 
-            var featureCollection = new FeatureCollection();
-            featureCollection.Set<IServerAddressesFeature>(new ServerAddressesFeature());
-            var server = new TestServer(builder, featureCollection);
+            var server = host.GetTestServer();
+            server.Features.Set<IServerAddressesFeature>(new ServerAddressesFeature());
 
             server.Features.Get<IServerAddressesFeature>().Addresses.Add("https://localhost:5050");
+            await host.StartAsync();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -259,7 +292,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                 TestSink.EnableWithTypeName<HttpsRedirectionMiddleware>,
                 TestSink.EnableWithTypeName<HttpsRedirectionMiddleware>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<ILoggerFactory>(loggerFactory);
@@ -272,14 +309,16 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                            return context.Response.WriteAsync("Hello world");
                        });
                    });
+                }).Build();
 
-            var featureCollection = new FeatureCollection();
-            featureCollection.Set<IServerAddressesFeature>(new ServerAddressesFeature());
-            var server = new TestServer(builder, featureCollection);
+            var server = host.GetTestServer();
+            server.Features.Set<IServerAddressesFeature>(new ServerAddressesFeature());
 
             server.Features.Get<IServerAddressesFeature>().Addresses.Add("https://localhost:5050");
             server.Features.Get<IServerAddressesFeature>().Addresses.Add("https://localhost:5051");
 
+            await host.StartAsync();
+
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -303,7 +342,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                 TestSink.EnableWithTypeName<HttpsRedirectionMiddleware>,
                 TestSink.EnableWithTypeName<HttpsRedirectionMiddleware>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<ILoggerFactory>(loggerFactory);
@@ -316,14 +359,15 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                            return context.Response.WriteAsync("Hello world");
                        });
                    });
+                }).Build();
 
-            var featureCollection = new FeatureCollection();
-            featureCollection.Set<IServerAddressesFeature>(new ServerAddressesFeature());
-            var server = new TestServer(builder, featureCollection);
-
+            var server = host.GetTestServer();
+            server.Features.Set<IServerAddressesFeature>(new ServerAddressesFeature());
             server.Features.Get<IServerAddressesFeature>().Addresses.Add("https://localhost:5050");
             server.Features.Get<IServerAddressesFeature>().Addresses.Add("https://example.com:5050");
 
+            await host.StartAsync();
+
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -351,7 +395,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                 TestSink.EnableWithTypeName<HttpsRedirectionMiddleware>,
                 TestSink.EnableWithTypeName<HttpsRedirectionMiddleware>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<ILoggerFactory>(loggerFactory);
@@ -364,8 +412,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                             return context.Response.WriteAsync("Hello world");
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
             var request = new HttpRequestMessage(HttpMethod.Get, "");
             var response = await client.SendAsync(request);
@@ -386,7 +437,11 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                 TestSink.EnableWithTypeName<HttpsRedirectionMiddleware>,
                 TestSink.EnableWithTypeName<HttpsRedirectionMiddleware>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<ILoggerFactory>(loggerFactory);
@@ -399,10 +454,12 @@ namespace Microsoft.AspNetCore.HttpsPolicy.Tests
                             return context.Response.WriteAsync("Hello world");
                         });
                     });
+                }).Build();
 
-            var featureCollection = new FeatureCollection();
-            featureCollection.Set<IServerAddressesFeature>(null);
-            var server = new TestServer(builder, featureCollection);
+            var server = host.GetTestServer();
+            server.Features.Set<IServerAddressesFeature>(null);
+
+            await host.StartAsync();
 
             var client = server.CreateClient();
             var request = new HttpRequestMessage(HttpMethod.Get, "");

src/Middleware/Localization.Routing/test/RouteDataRequestCultureProviderTest.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.Collections.Generic;
@@ -11,6 +11,7 @@ using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Routing;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Localization.Routing
@@ -30,7 +31,11 @@ namespace Microsoft.AspNetCore.Localization.Routing
             string expectedCulture,
             string expectedUICulture)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRouter(routes =>
@@ -72,8 +77,11 @@ namespace Microsoft.AspNetCore.Localization.Routing
                     {
                         services.AddRouting();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(requestUrl);
@@ -87,7 +95,11 @@ namespace Microsoft.AspNetCore.Localization.Routing
         [Fact]
         public async Task GetDefaultCultureInfo_IfCultureKeysAreMissing()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         var options = new RequestLocalizationOptions
@@ -111,8 +123,11 @@ namespace Microsoft.AspNetCore.Localization.Routing
                                         $"{requestCulture.Culture.Name},{requestCulture.UICulture.Name}");
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync("/page");
@@ -135,7 +150,11 @@ namespace Microsoft.AspNetCore.Localization.Routing
             string expectedCulture,
             string expectedUICulture)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRouter(routes =>
@@ -180,8 +199,11 @@ namespace Microsoft.AspNetCore.Localization.Routing
                     {
                         services.AddRouting();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(requestUrl);

src/Middleware/Localization/sample/Startup.cs

@@ -3,12 +3,14 @@
 
 using System;
 using System.Globalization;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Localization;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Localization;
 using Microsoft.Extensions.Logging;
 
@@ -134,21 +136,25 @@ $@"<!doctype html>
             await context.Response.WriteAsync($"    <option value=\"pp-NOTREAL\">Made-up (Not a real anything)</option>");
         }
 
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
             var config = new ConfigurationBuilder()
                 .AddCommandLine(args)
                 .Build();
 
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .ConfigureLogging(factory => factory.AddConsole())
                     .UseKestrel()
                     .UseConfiguration(config)
                     .UseIISIntegration()
-                .UseStartup<Startup>()
+                    .UseStartup<Startup>();
+                })
                 .Build();
 
-            host.Run();
+            return host.RunAsync();
         }
     }
 }

src/Middleware/Localization/test/FunctionalTests/LocalizationSampleTest.cs

@@ -9,6 +9,7 @@ using System.Threading.Tasks;
 using LocalizationSample;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.TestHost;
+using Microsoft.Extensions.Hosting;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Localization.FunctionalTests
@@ -19,8 +20,17 @@ namespace Microsoft.AspNetCore.Localization.FunctionalTests
         public async Task LocalizationSampleSmokeTest()
         {
             // Arrange
-            var webHostBuilder = new WebHostBuilder().UseStartup(typeof(Startup));
-            var testHost = new TestServer(webHostBuilder);
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
+                    .UseStartup(typeof(Startup));
+                }).Build();
+
+            await host.StartAsync();
+
+            var testHost = host.GetTestServer();
             var locale = "fr-FR";
             var client = testHost.CreateClient();
             var request = new HttpRequestMessage(HttpMethod.Get, "My/Resources");

src/Middleware/Localization/test/FunctionalTests/LocalizationTest.cs

@@ -8,6 +8,7 @@ using System.Threading.Tasks;
 using LocalizationWebsite;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.TestHost;
+using Microsoft.Extensions.Hosting;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Localization.FunctionalTests
@@ -97,8 +98,17 @@ namespace Microsoft.AspNetCore.Localization.FunctionalTests
 
         private async Task RunTest(Type startupType, string culture, string expected)
         {
-            var webHostBuilder = new WebHostBuilder().UseStartup(startupType);
-            var testHost = new TestServer(webHostBuilder);
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
+                    .UseStartup(startupType);
+                }).Build();
+
+            await host.StartAsync();
+
+            var testHost = host.GetTestServer();
 
             var client = testHost.CreateClient();
             var request = new HttpRequestMessage();

src/Middleware/Localization/test/UnitTests/AcceptLanguageHeaderRequestCultureProviderTest.cs

@@ -8,6 +8,7 @@ using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Localization;
 using Microsoft.AspNetCore.TestHost;
+using Microsoft.Extensions.Hosting;
 using Xunit;
 
 namespace Microsoft.Extensions.Localization
@@ -17,7 +18,11 @@ namespace Microsoft.Extensions.Localization
         [Fact]
         public async Task GetFallbackLanguage_ReturnsFirstNonNullCultureFromSupportedCultureList()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRequestLocalization(new RequestLocalizationOptions
@@ -37,8 +42,11 @@ namespace Microsoft.Extensions.Localization
                             return Task.FromResult(0);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 client.DefaultRequestHeaders.AcceptLanguage.ParseAdd("jp,ar-SA,en-US");
@@ -51,7 +59,11 @@ namespace Microsoft.Extensions.Localization
         [Fact]
         public async Task GetFallbackLanguage_ReturnsFromSupportedCulture_AcceptLanguageListContainsSupportedCultures()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRequestLocalization(new RequestLocalizationOptions
@@ -71,8 +83,11 @@ namespace Microsoft.Extensions.Localization
                             return Task.FromResult(0);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 client.DefaultRequestHeaders.AcceptLanguage.ParseAdd("en-GB,ar-SA,en-US");
@@ -84,7 +99,11 @@ namespace Microsoft.Extensions.Localization
         [Fact]
         public async Task GetFallbackLanguage_ReturnsDefault_AcceptLanguageListDoesnotContainSupportedCultures()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRequestLocalization(new RequestLocalizationOptions
@@ -104,8 +123,11 @@ namespace Microsoft.Extensions.Localization
                             return Task.FromResult(0);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 client.DefaultRequestHeaders.AcceptLanguage.ParseAdd("en-GB,ar-MA,en-US");
@@ -118,7 +140,11 @@ namespace Microsoft.Extensions.Localization
         [Fact]
         public async Task OmitDefaultRequestCultureShouldNotThrowNullReferenceException_And_ShouldGetTheRightCulture()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRequestLocalization(new RequestLocalizationOptions
@@ -143,8 +169,11 @@ namespace Microsoft.Extensions.Localization
                             return Task.FromResult(0);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 client.DefaultRequestHeaders.AcceptLanguage.ParseAdd("en-GB,ar-YE,en-US");

src/Middleware/Localization/test/UnitTests/CookieRequestCultureProviderTest.cs

@@ -9,6 +9,7 @@ using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Localization;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Logging.Testing;
 using Microsoft.Net.Http.Headers;
@@ -21,7 +22,11 @@ namespace Microsoft.Extensions.Localization
         [Fact]
         public async Task GetCultureInfoFromPersistentCookie()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         var options = new RequestLocalizationOptions
@@ -51,8 +56,11 @@ namespace Microsoft.Extensions.Localization
                             return Task.FromResult(0);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var culture = new CultureInfo("ar-SA");
@@ -67,7 +75,11 @@ namespace Microsoft.Extensions.Localization
         [Fact]
         public async Task GetDefaultCultureInfoIfCultureKeysAreMissingOrInvalid()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         var options = new RequestLocalizationOptions
@@ -96,8 +108,11 @@ namespace Microsoft.Extensions.Localization
                             return Task.FromResult(0);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
 
@@ -109,7 +124,11 @@ namespace Microsoft.Extensions.Localization
         [Fact]
         public async Task GetDefaultCultureInfoIfCookieDoesNotExist()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         var options = new RequestLocalizationOptions
@@ -138,8 +157,11 @@ namespace Microsoft.Extensions.Localization
                             return Task.FromResult(0);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -153,7 +175,11 @@ namespace Microsoft.Extensions.Localization
                 TestSink.EnableWithTypeName<RequestLocalizationMiddleware>,
                 TestSink.EnableWithTypeName<RequestLocalizationMiddleware>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         var options = new RequestLocalizationOptions
@@ -180,8 +206,11 @@ namespace Microsoft.Extensions.Localization
                     {
                         services.AddSingleton(typeof(ILoggerFactory), loggerFactory);
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var culture = "??";
@@ -206,7 +235,11 @@ namespace Microsoft.Extensions.Localization
                 TestSink.EnableWithTypeName<RequestLocalizationMiddleware>,
                 TestSink.EnableWithTypeName<RequestLocalizationMiddleware>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         var options = new RequestLocalizationOptions
@@ -233,8 +266,11 @@ namespace Microsoft.Extensions.Localization
                     {
                         services.AddSingleton(typeof(ILoggerFactory), loggerFactory);
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var culture = "ar-YE";

src/Middleware/Localization/test/UnitTests/CustomRequestCultureProviderTest.cs

@@ -10,6 +10,7 @@ using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Localization;
 using Microsoft.AspNetCore.TestHost;
+using Microsoft.Extensions.Hosting;
 using Xunit;
 
 namespace Microsoft.Extensions.Localization
@@ -19,7 +20,11 @@ namespace Microsoft.Extensions.Localization
         [Fact]
         public async Task CustomRequestCultureProviderThatGetsCultureInfoFromUrl()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         var options = new RequestLocalizationOptions
@@ -49,8 +54,11 @@ namespace Microsoft.Extensions.Localization
                             return Task.FromResult(0);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync("/ar/page");

src/Middleware/Localization/test/UnitTests/QueryStringRequestCultureProviderTest.cs

@@ -8,6 +8,7 @@ using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Localization;
 using Microsoft.AspNetCore.TestHost;
+using Microsoft.Extensions.Hosting;
 using Xunit;
 
 namespace Microsoft.Extensions.Localization
@@ -17,7 +18,11 @@ namespace Microsoft.Extensions.Localization
         [Fact]
         public async Task GetCultureInfoFromQueryString()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRequestLocalization(new RequestLocalizationOptions
@@ -41,8 +46,11 @@ namespace Microsoft.Extensions.Localization
                             return Task.FromResult(0);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync("/page?culture=ar-SA&ui-culture=ar-YE");
@@ -52,7 +60,11 @@ namespace Microsoft.Extensions.Localization
         [Fact]
         public async Task GetDefaultCultureInfoIfCultureKeysAreMissing()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRequestLocalization(new RequestLocalizationOptions
@@ -68,8 +80,11 @@ namespace Microsoft.Extensions.Localization
                             return Task.FromResult(0);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync("/page");
@@ -79,7 +94,11 @@ namespace Microsoft.Extensions.Localization
         [Fact]
         public async Task GetDefaultCultureInfoIfCultureIsInSupportedCultureList()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRequestLocalization(new RequestLocalizationOptions
@@ -102,8 +121,11 @@ namespace Microsoft.Extensions.Localization
                             return Task.FromResult(0);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync("/page?culture=ar-XY&ui-culture=ar-SA");
@@ -113,7 +135,11 @@ namespace Microsoft.Extensions.Localization
         [Fact]
         public async Task GetDefaultCultureInfoIfUICultureIsNotInSupportedList()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRequestLocalization(new RequestLocalizationOptions
@@ -136,8 +162,11 @@ namespace Microsoft.Extensions.Localization
                             return Task.FromResult(0);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync("/page?culture=ar-SA&ui-culture=ar-XY");
@@ -147,7 +176,11 @@ namespace Microsoft.Extensions.Localization
         [Fact]
         public async Task GetSameCultureInfoIfCultureKeyIsMissing()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRequestLocalization(new RequestLocalizationOptions
@@ -171,8 +204,11 @@ namespace Microsoft.Extensions.Localization
                             return Task.FromResult(0);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync("/page?ui-culture=ar-SA");
@@ -182,7 +218,11 @@ namespace Microsoft.Extensions.Localization
         [Fact]
         public async Task GetSameCultureInfoIfUICultureKeyIsMissing()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRequestLocalization(new RequestLocalizationOptions
@@ -206,8 +246,11 @@ namespace Microsoft.Extensions.Localization
                             return Task.FromResult(0);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync("/page?culture=ar-SA");
@@ -217,7 +260,11 @@ namespace Microsoft.Extensions.Localization
         [Fact]
         public async Task GetCultureInfoFromQueryStringWithCustomKeys()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         var options = new RequestLocalizationOptions
@@ -246,8 +293,11 @@ namespace Microsoft.Extensions.Localization
                             return Task.FromResult(0);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync("/page?c=ar-SA&uic=ar-YE");
@@ -257,7 +307,11 @@ namespace Microsoft.Extensions.Localization
         [Fact]
         public async Task GetTheRightCultureInfoRegardlessOfCultureNameCasing()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         var options = new RequestLocalizationOptions
@@ -287,8 +341,11 @@ namespace Microsoft.Extensions.Localization
                             return Task.FromResult(0);
                         });
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync("/page?c=FR&uic=FR");

src/Middleware/Localization/testassets/LocalizationWebsite/Program.cs

@@ -1,21 +1,26 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 
 namespace LocalizationWebsite
 {
     public static class Program
     {
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
             var config = new ConfigurationBuilder()
                 .AddCommandLine(args)
                 .Build();
 
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .ConfigureLogging((_, factory) =>
                     {
                         factory.AddConsole();
@@ -23,10 +28,11 @@ namespace LocalizationWebsite
                     })
                     .UseKestrel()
                     .UseConfiguration(config)
-                .UseStartup("LocalizationWebsite")
+                    .UseStartup("LocalizationWebsite");
+                })
                 .Build();
 
-            host.Run();
+            return host.RunAsync();
         }
     }
 }

src/Middleware/MiddlewareAnalysis/samples/MiddlewareAnalysisSample/Startup.cs

@@ -1,10 +1,12 @@
 using System;
 using System.Diagnostics;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.DiagnosticAdapter;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 
 namespace MiddlewareAnaysisSample
@@ -79,9 +81,12 @@ namespace MiddlewareAnaysisSample
             // Note there's always a default 404 middleware at the end of the pipeline.
         }
 
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .ConfigureLogging((_, factory) =>
                     {
                         factory.AddConsole();
@@ -89,10 +94,10 @@ namespace MiddlewareAnaysisSample
                     })
                     .UseKestrel()
                     .UseIISIntegration()
-                .UseStartup<Startup>()
-                .Build();
+                    .UseStartup<Startup>();
+                }).Build();
 
-            host.Run();
+            return host.RunAsync();
         }
 
         public class TestDiagnosticListener

src/Middleware/MiddlewareAnalysis/test/MiddlewareAnalysisTests.cs

@@ -8,6 +8,7 @@ using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Xunit;
 
 namespace Microsoft.AspNetCore.MiddlewareAnalysis
@@ -19,7 +20,11 @@ namespace Microsoft.AspNetCore.MiddlewareAnalysis
         {
             DiagnosticListener diagnosticListener = null;
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         diagnosticListener = app.ApplicationServices.GetRequiredService<DiagnosticListener>();
@@ -31,7 +36,11 @@ namespace Microsoft.AspNetCore.MiddlewareAnalysis
                         });
                     })
                     .ConfigureServices(services => services.AddMiddlewareAnalysis());
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var listener = new TestDiagnosticListener();
             diagnosticListener.SubscribeWithAdapter(listener);

src/Middleware/NodeServices/samples/NodeServicesExamples/Startup.cs

@@ -3,11 +3,13 @@
 
 using System;
 using System.IO;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.NodeServices;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 
 namespace NodeServicesExamples
@@ -58,9 +60,12 @@ namespace NodeServicesExamples
         }
 #pragma warning restore 0618
 
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .ConfigureLogging(factory =>
                     {
                         factory.AddConsole();
@@ -69,10 +74,10 @@ namespace NodeServicesExamples
                     .UseContentRoot(Directory.GetCurrentDirectory())
                     .UseIISIntegration()
                     .UseKestrel()
-                .UseStartup<Startup>()
-                .Build();
+                    .UseStartup<Startup>();
+                }).Build();
 
-            host.Run();
+            return host.RunAsync();
         }
     }
 }

src/Middleware/ResponseCaching/samples/ResponseCachingSample/Startup.cs

@@ -3,10 +3,12 @@
 
 using System;
 using System.IO;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Net.Http.Headers;
 
 namespace ResponseCachingSample
@@ -34,16 +36,19 @@ namespace ResponseCachingSample
             });
         }
 
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .UseKestrel()
                     .UseContentRoot(Directory.GetCurrentDirectory())
                     .UseIISIntegration()
-                .UseStartup<Startup>()
-                .Build();
+                    .UseStartup<Startup>();
+                }).Build();
 
-            host.Run();
+            return host.RunAsync();
         }
     }
 }

src/Middleware/ResponseCaching/test/ResponseCachingTests.cs

@@ -22,7 +22,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.SendAsync(TestUtils.CreateRequest(method, ""));
@@ -42,7 +46,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.SendAsync(TestUtils.CreateRequest(method, ""));
@@ -60,7 +68,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.PostAsync("", new StringContent(string.Empty));
@@ -78,7 +90,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var subsequentResponse = await client.SendAsync(new HttpRequestMessage(HttpMethod.Head, ""));
@@ -96,7 +112,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.SendAsync(new HttpRequestMessage(HttpMethod.Get, ""));
@@ -116,7 +136,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
 
@@ -145,7 +169,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
 
@@ -174,7 +202,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.SendAsync(TestUtils.CreateRequest(method, "path"));
@@ -194,7 +226,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.SendAsync(TestUtils.CreateRequest(method, "?Expires=0"));
@@ -214,7 +250,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     client.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("abc");
@@ -233,7 +273,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     client.DefaultRequestHeaders.From = "user@example.com";
@@ -252,7 +296,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     client.DefaultRequestHeaders.From = "user@example.com";
@@ -272,7 +320,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("?query=value");
@@ -290,7 +342,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("?querya=valuea&queryb=valueb");
@@ -308,7 +364,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("?querya=valuea&queryb=valueb");
@@ -326,7 +386,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("?QueryA=ValueA&QueryB=ValueB");
@@ -344,7 +408,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("?QueryA=ValueA&QueryB=ValueB");
@@ -362,7 +430,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("?query=value");
@@ -380,7 +452,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("?querya=valuea&queryb=valueb");
@@ -398,7 +474,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("?querya=valuea&queryb=valueb");
@@ -416,7 +496,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("");
@@ -438,7 +522,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("");
@@ -461,7 +549,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("");
@@ -479,7 +571,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("");
@@ -501,7 +597,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     client.DefaultRequestHeaders.CacheControl = new System.Net.Http.Headers.CacheControlHeaderValue()
@@ -523,7 +623,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("");
@@ -546,7 +650,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("?Expires=90");
@@ -567,7 +675,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("");
@@ -591,7 +703,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("?Expires=90");
@@ -612,7 +728,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("");
@@ -634,7 +754,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("");
@@ -655,7 +779,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("");
@@ -676,7 +804,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.GetAsync("/path");
@@ -694,7 +826,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     client.DefaultRequestHeaders.From = "user@example.com";
@@ -716,7 +852,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     client.DefaultRequestHeaders.From = "user@example.com";
@@ -747,7 +887,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     client.DefaultRequestHeaders.From = "user@example.com";
@@ -778,7 +922,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
 
             foreach (var builder in builders)
             {
-                using (var server = new TestServer(builder))
+                using var host = builder.Build();
+
+                await host.StartAsync();
+
+                using (var server = host.GetTestServer())
                 {
                     var client = server.CreateClient();
                     var initialResponse = await client.SendAsync(TestUtils.CreateRequest("HEAD", "?contentLength=10"));

src/Middleware/ResponseCaching/test/TestUtils.cs

@@ -12,7 +12,9 @@ using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Features;
+using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Logging.Abstractions;
 using Microsoft.Extensions.Logging.Testing;
@@ -116,7 +118,7 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
             return new ResponseCachingKeyProvider(new DefaultObjectPoolProvider(), Options.Create(options));
         }
 
-        internal static IEnumerable<IWebHostBuilder> CreateBuildersWithResponseCaching(
+        internal static IEnumerable<IHostBuilder> CreateBuildersWithResponseCaching(
             Action<IApplicationBuilder> configureDelegate = null,
             ResponseCachingOptions options = null,
             Action<HttpContext> contextAction = null)
@@ -141,7 +143,7 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
                 });
         }
 
-        private static IEnumerable<IWebHostBuilder> CreateBuildersWithResponseCaching(
+        private static IEnumerable<IHostBuilder> CreateBuildersWithResponseCaching(
             Action<IApplicationBuilder> configureDelegate = null,
             ResponseCachingOptions options = null,
             IEnumerable<RequestDelegate> requestDelegates = null)
@@ -162,7 +164,11 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
             foreach (var requestDelegate in requestDelegates)
             {
                 // Test with in memory ResponseCache
-                yield return new WebHostBuilder()
+                yield return new HostBuilder()
+                    .ConfigureWebHost(webHostBuilder =>
+                    {
+                        webHostBuilder
+                        .UseTestServer()
                         .ConfigureServices(services =>
                         {
                             services.AddResponseCaching(responseCachingOptions =>
@@ -181,6 +187,7 @@ namespace Microsoft.AspNetCore.ResponseCaching.Tests
                             app.UseResponseCaching();
                             app.Run(requestDelegate);
                         });
+                    });
             }
         }
 

src/Middleware/ResponseCompression/sample/Startup.cs

@@ -11,6 +11,7 @@ using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.ResponseCompression;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 
 namespace ResponseCompressionSample
@@ -71,19 +72,22 @@ namespace ResponseCompressionSample
             });
         }
 
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .UseKestrel()
                     .ConfigureLogging(factory =>
                     {
                         factory.AddConsole()
                             .SetMinimumLevel(LogLevel.Debug);
                     })
-                .UseStartup<Startup>()
-                .Build();
+                    .UseStartup<Startup>();
+                }).Build();
 
-            host.Run();
+            return host.RunAsync();
         }
     }
 }

src/Middleware/ResponseCompression/test/ResponseCompressionMiddlewareTest.cs

@@ -17,6 +17,7 @@ using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.AspNetCore.Testing;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Logging.Testing;
 using Microsoft.Net.Http.Headers;
@@ -134,7 +135,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
         [Fact]
         public async Task GZipCompressionProvider_OptionsSetInDI_Compress()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.Configure<GzipCompressionProviderOptions>(options => options.Level = CompressionLevel.NoCompression);
@@ -150,8 +155,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                             return context.Response.WriteAsync(new string('a', 100));
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -286,7 +294,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
         [InlineData("text/plain2")]
         public async Task NoBody_NotCompressed(string contentType)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddResponseCompression();
@@ -301,8 +313,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                             return Task.FromResult(0);
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -413,7 +428,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                 TestSink.EnableWithTypeName<ResponseCompressionProvider>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<ILoggerFactory>(loggerFactory);
@@ -432,11 +451,12 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                             return context.Response.WriteAsync(new string('a', 100));
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder)
-            {
-                BaseAddress = new Uri("https://localhost/")
-            };
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
+            server.BaseAddress = new Uri("https://localhost/");
 
             var client = server.CreateClient();
 
@@ -469,7 +489,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                 TestSink.EnableWithTypeName<ResponseCompressionProvider>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<ILoggerFactory>(loggerFactory);
@@ -490,11 +514,12 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                             return context.Response.WriteAsync(new string('a', 100));
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder)
-            {
-                BaseAddress = new Uri("https://localhost/")
-            };
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
+            server.BaseAddress = new Uri("https://localhost/");
 
             var client = server.CreateClient();
 
@@ -527,7 +552,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                 TestSink.EnableWithTypeName<ResponseCompressionProvider>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddSingleton<ILoggerFactory>(loggerFactory);
@@ -548,11 +577,12 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                             return context.Response.WriteAsync(new string('a', 100));
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder)
-            {
-                BaseAddress = new Uri("https://localhost/")
-            };
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
+            server.BaseAddress = new Uri("https://localhost/");
 
             var client = server.CreateClient();
 
@@ -580,7 +610,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
         {
             var responseReceived = new TaskCompletionSource<int>(TaskCreationOptions.RunContinuationsAsynchronously);
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddResponseCompression();
@@ -597,11 +631,12 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                             await context.Response.WriteAsync(new string('a', 100));
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder)
-            {
-                AllowSynchronousIO = true // needed for synchronous flush
-            };
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
+            server.AllowSynchronousIO = true; // needed for synchronous flush
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -621,7 +656,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
         {
             var responseReceived = new TaskCompletionSource<int>(TaskCreationOptions.RunContinuationsAsynchronously);
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddResponseCompression();
@@ -638,8 +677,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                             await context.Response.WriteAsync(new string('a', 100));
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -659,7 +701,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
         {
             var responseReceived = new TaskCompletionSource<int>(TaskCreationOptions.RunContinuationsAsynchronously);
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddResponseCompression();
@@ -683,8 +729,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                             context.Response.Body.Write(new byte[90], 0, 90);
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -711,7 +760,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
         {
             var responseReceived = new TaskCompletionSource<int>(TaskCreationOptions.RunContinuationsAsynchronously);
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddResponseCompression();
@@ -729,8 +782,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                             await context.Response.WriteAsync(new string('a', 90));
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -764,7 +820,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                 new TaskCompletionSource<int>(TaskCreationOptions.RunContinuationsAsynchronously),
             };
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddResponseCompression();
@@ -792,8 +852,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                             }
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -827,7 +890,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                 new TaskCompletionSource<int>(TaskCreationOptions.RunContinuationsAsynchronously),
             };
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddResponseCompression();
@@ -849,8 +916,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                             }
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -876,7 +946,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
         {
             FakeSendFileFeature fakeSendFile = null;
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddResponseCompression();
@@ -900,8 +974,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                             return sendFile.SendFileAsync("testfile1kb.txt", 0, null, CancellationToken.None);
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -919,7 +996,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
         {
             FakeSendFileFeature fakeSendFile = null;
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddResponseCompression();
@@ -943,8 +1024,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                             return sendFile.SendFileAsync("testfile1kb.txt", 0, null, CancellationToken.None);
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -962,7 +1046,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
         {
             FakeSendFileFeature fakeSendFile = null;
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddResponseCompression();
@@ -986,8 +1074,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                             await feature.SendFileAsync("testfile1kb.txt", 0, null, CancellationToken.None);
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -1006,7 +1097,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
         {
             var responseReceived = new TaskCompletionSource<int>(TaskCreationOptions.RunContinuationsAsynchronously);
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddResponseCompression();
@@ -1029,8 +1124,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                             await context.Response.WriteAsync(new string('a', 90));
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -1063,7 +1161,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                 TestSink.EnableWithTypeName<ResponseCompressionProvider>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
 
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.AddResponseCompression(configure ?? (_ => { }));
@@ -1080,8 +1182,11 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                             return context.Response.WriteAsync(new string('a', uncompressedBodyLength));
                         });
                     });
+                }).Build();
 
-            var server = new TestServer(builder);
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
             var client = server.CreateClient();
 
             var request = new HttpRequestMessage(HttpMethod.Get, "");
@@ -1090,7 +1195,9 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
                 request.Headers.AcceptEncoding.Add(System.Net.Http.Headers.StringWithQualityHeaderValue.Parse(requestAcceptEncodings[i]));
             }
 
-            return (await client.SendAsync(request), sink.Writes.ToList());
+            var response = await client.SendAsync(request);
+
+            return (response, sink.Writes.ToList());
         }
 
         private void CheckResponseCompressed(HttpResponseMessage response, int expectedBodyLength, string expectedEncoding)

src/Middleware/Rewrite/sample/Startup.cs

@@ -3,11 +3,13 @@
 
 using System.IO;
 using System.Net;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Rewrite;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 
 namespace RewriteSample
 {
@@ -42,9 +44,12 @@ namespace RewriteSample
             });
         }
 
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .UseKestrel(options =>
                     {
                         options.Listen(IPAddress.Loopback, 5000);
@@ -55,10 +60,10 @@ namespace RewriteSample
                         });
                     })
                     .UseStartup<Startup>()
-                .UseContentRoot(Directory.GetCurrentDirectory())
-                .Build();
+                    .UseContentRoot(Directory.GetCurrentDirectory());
+                }).Build();
 
-            host.Run();
+            return host.RunAsync();
         }
     }
 }

src/Middleware/Rewrite/test/ApacheModRewrite/ModRewriteMiddlewareTest.cs

@@ -9,6 +9,7 @@ using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.TestHost;
+using Microsoft.Extensions.Hosting;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
@@ -19,13 +20,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
         public async Task Invoke_RewritePathWhenMatching()
         {
             var options = new RewriteOptions().AddApacheModRewrite(new StringReader("RewriteRule /hey/(.*) /$1 "));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(context.Request.Path));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync("/hey/hello");
 
@@ -37,13 +46,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
         {
             var options = new RewriteOptions().AddApacheModRewrite(new StringReader("RewriteRule /hey/(.*) /$1 [L]"))
                             .AddApacheModRewrite(new StringReader("RewriteRule /hello /what"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                      .Configure(app =>
                      {
                          app.UseRewriter(options);
                          app.Run(context => context.Response.WriteAsync(context.Request.Path));
                      });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync("/hey/hello");
 
@@ -55,13 +72,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
         {
             var options = new RewriteOptions().AddApacheModRewrite(new StringReader("RewriteRule /hey/(.*) /$1"))
                                        .AddApacheModRewrite(new StringReader("RewriteRule /hello /what"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(context.Request.Path));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync("/hey/hello");
 
@@ -72,13 +97,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
         public async Task Invoke_ShouldIgnoreComments()
         {
             var options = new RewriteOptions().AddApacheModRewrite(new StringReader("#RewriteRule ^/hey/(.*) /$1 "));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(context.Request.Path));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync("/hey/hello");
 
@@ -89,13 +122,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
         public async Task Invoke_ShouldRewriteHomepage()
         {
             var options = new RewriteOptions().AddApacheModRewrite(new StringReader(@"RewriteRule ^/$ /homepage.html"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(context.Request.Path));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync("http://www.foo.org/");
 
@@ -106,13 +147,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
         public async Task Invoke_ShouldIgnorePorts()
         {
             var options = new RewriteOptions().AddApacheModRewrite(new StringReader(@"RewriteRule ^/$ /homepage.html"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                    .Configure(app =>
                    {
                        app.UseRewriter(options);
                        app.Run(context => context.Response.WriteAsync(context.Request.Path));
                    });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync("http://www.foo.org:42/");
 
@@ -123,13 +172,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
         public async Task Invoke_HandleNegatedRewriteRules()
         {
             var options = new RewriteOptions().AddApacheModRewrite(new StringReader(@"RewriteRule !^/$ /homepage.html"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                    .Configure(app =>
                    {
                        app.UseRewriter(options);
                        app.Run(context => context.Response.WriteAsync(context.Request.Path));
                    });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync("http://www.foo.org/");
 
@@ -142,13 +199,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
         public async Task Invoke_BackReferencesShouldBeApplied(string url, string rule, string expected)
         {
             var options = new RewriteOptions().AddApacheModRewrite(new StringReader(rule));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(context.Request.Path));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync(url);
 
@@ -165,13 +230,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
         public async Task Invoke_ShouldHandleFlagNoCase(string url, string rule, string expected)
         {
             var options = new RewriteOptions().AddApacheModRewrite(new StringReader(rule));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(context.Request.Path));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync(url);
 
@@ -183,13 +256,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
         {
             var options = new RewriteOptions()
                 .AddApacheModRewrite(new StringReader(@"RewriteRule (.+) http://www.example.com$1/"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(context.Request.Path));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync("http://www.foo.org/blog/2016-jun");
 
@@ -201,13 +282,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
         {
             var options = new RewriteOptions()
                 .AddApacheModRewrite(new StringReader(@"RewriteRule (.+) http://www.example.com$1/"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(context.Request.Scheme + "://" + context.Request.Host.Host + context.Request.Path + context.Request.QueryString));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync("http://www.foo.org/blog/2016-jun");
 
@@ -219,13 +308,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
         {
             var options = new RewriteOptions()
                 .AddApacheModRewrite(new StringReader(@"RewriteRule (.+) http://www.example.com$1/"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(context.Request.Scheme + "://" + context.Request.Host.Host + context.Request.Path + context.Request.QueryString));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync("http://www.foo.org/blog/2016-jun");
 
@@ -238,13 +335,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
         {
             var options = new RewriteOptions()
                 .AddApacheModRewrite(new StringReader("RewriteCond %{REQUEST_URI} /foo/  \nRewriteCond %{HTTPS} !on   \nRewriteRule ^(.*)$ https://www.example.com$1 [R=301,L]"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(context.Request.Scheme + "://" + context.Request.Host.Host + context.Request.Path + context.Request.QueryString));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync(input);
 
@@ -258,13 +363,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
         {
             var options = new RewriteOptions()
                 .AddApacheModRewrite(new StringReader("RewriteRule ^(.*)$ $1 [R=301,L]"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(context.Request.Scheme + "://" + context.Request.Host.Host + context.Request.Path + context.Request.QueryString));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync(input);
 
@@ -278,13 +391,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
         {
             var options = new RewriteOptions()
                 .AddApacheModRewrite(new StringReader("RewriteRule ^(.*)$ $1 [L]"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(context.Request.Path + context.Request.QueryString));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync(input);
             Assert.Equal("/", response);
@@ -294,7 +415,11 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
         public async Task Invoke_CaptureEmptyStringInRegexAssertLocationHeaderContainsPathBase()
         {
             var options = new RewriteOptions().AddApacheModRewrite(new StringReader(@"RewriteRule ^(.*)$ $1 [R=301,L]"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
@@ -302,7 +427,12 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
                             context.Request.Path +
                             context.Request.QueryString));
                     });
-            var server = new TestServer(builder) { BaseAddress = new Uri("http://localhost:5000/foo") };
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
+            server.BaseAddress = new Uri("http://localhost:5000/foo");
 
             var response = await server.CreateClient().GetAsync("");
 
@@ -315,15 +445,24 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.ModRewrite
             var options = new RewriteOptions().AddApacheModRewrite(new StringReader(@"RewriteCond %{REQUEST_URI} /home
 RewriteCond %{QUERY_STRING} report_id=(.+)
 RewriteRule (.*) http://localhost:80/home/report/%1 [R=301,L,QSD]"));
-            var builder = new WebHostBuilder().Configure(app =>
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
+                    .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(
                            context.Request.Path +
                            context.Request.QueryString));
                     });
+                }).Build();
 
-            var server = new TestServer(builder) { BaseAddress = new Uri("http://localhost:5000/foo") };
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
+            server.BaseAddress = new Uri("http://localhost:5000/foo");
             var response = await server.CreateClient().GetAsync("/home?report_id=123");
 
             Assert.Equal("http://localhost:80/home/report/123", response.Headers.Location.OriginalString);

src/Middleware/Rewrite/test/IISUrlRewrite/MiddleWareTests.cs

@@ -15,6 +15,7 @@ using Microsoft.AspNetCore.Rewrite.IISUrlRewrite;
 using Microsoft.AspNetCore.Rewrite.UrlActions;
 using Microsoft.AspNetCore.Rewrite.UrlMatches;
 using Microsoft.AspNetCore.TestHost;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Net.Http.Headers;
 using Xunit;
 
@@ -33,13 +34,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                 </rule>
                 </rules>
                 </rewrite>"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                 .ConfigureWebHost(webHostBuilder =>
+                 {
+                     webHostBuilder
+                     .UseTestServer()
                      .Configure(app =>
                      {
                          app.UseRewriter(options);
                          app.Run(context => context.Response.WriteAsync(context.Response.Headers[HeaderNames.Location]));
                      });
-            var server = new TestServer(builder);
+                 }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync("article/10/hey");
 
@@ -57,13 +66,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                 </rule>
                 </rules>
                 </rewrite>"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(context.Request.Path + context.Request.QueryString));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync("/article/10/hey");
 
@@ -85,13 +102,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                 </rule>
                 </rules>
                 </rewrite>"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(context.Request.Path + context.Request.QueryString));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync("page.asp?p2=321&p1=123");
 
@@ -109,13 +134,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                 </rule>
                 </rules>
                 </rewrite>"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(context.Response.Headers[HeaderNames.Location]));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync("HElLo");
 
@@ -137,12 +170,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                 </rule>
                 </rules>
                 </rewrite>"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync("hey/hello/");
 
@@ -164,12 +205,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                 </rule>
                 </rules>
                 </rewrite>"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync("hey/hello");
 
@@ -190,12 +239,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                 </rule>
                 </rules>
                 </rewrite>"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync(new Uri("http://example.com"));
 
@@ -216,7 +273,11 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                 </rule>
                 </rules>
                 </rewrite>"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
@@ -227,7 +288,11 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                             context.Request.Path +
                             context.Request.QueryString));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync(new Uri("http://example.com"));
 
@@ -245,7 +310,11 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                 </rule>
                 </rules>
                 </rewrite>"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
@@ -256,7 +325,11 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                             context.Request.Path +
                             context.Request.QueryString));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync(new Uri("http://example.com/"));
 
@@ -274,7 +347,11 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                 </rule>
                 </rules>
                 </rewrite>"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
@@ -285,7 +362,11 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                             context.Request.Path +
                             context.Request.QueryString));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync(new Uri("http://example.com/"));
 
@@ -303,7 +384,11 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                 </rule>
                 </rules>
                 </rewrite>"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
@@ -311,7 +396,11 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                             context.Request.Path +
                             context.Request.QueryString));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync(new Uri("http://example.com/"));
 
@@ -329,7 +418,11 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                 </rule>
                 </rules>
                 </rewrite>"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
@@ -337,7 +430,12 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                                 context.Request.Path +
                                 context.Request.QueryString));
                     });
-            var server = new TestServer(builder) { BaseAddress = new Uri("http://localhost:5000/foo") };
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
+            server.BaseAddress = new Uri("http://localhost:5000/foo");
 
             var response = await server.CreateClient().GetAsync("");
 
@@ -362,12 +460,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                 </rule>
                 </rules>
                 </rewrite>"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync("hey/hello");
 
@@ -390,12 +496,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                 </rule>
                 </rules>
                 </rewrite>"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync("article/23?p1=123&p2=abc");
 
@@ -418,12 +532,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                 </rule>
                 </rules>
                 </rewrite>"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync("article/23?p1=123&p2=abc");
 
@@ -447,12 +569,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                 </rule>
                 </rules>
                 </rewrite>"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var ex = await Assert.ThrowsAsync<IndexOutOfRangeException>(() => server.CreateClient().GetAsync("article/23?p1=123&p2=abc"));
 
@@ -475,13 +605,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                             </globalRules>
                         </rewrite>";
             var options = new RewriteOptions().AddIISUrlRewrite(new StringReader(xml));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(context.Request.GetEncodedUrl()));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             // act
             var response = await server.CreateClient().GetStringAsync($"http://localhost/{Guid.NewGuid()}/foo/bar");
@@ -512,13 +650,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                         </rewriteMap>
                     </rewriteMaps>
                 </rewrite>"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(context.Request.GetEncodedUrl()));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync(new Uri(requestUri));
 
@@ -536,12 +682,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
                 </rule>
                 </rules>
                 </rewrite>"));
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync("article/10/hey");
             var content = await response.Content.ReadAsStringAsync();
@@ -583,13 +737,21 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.UrlRewrite
             ruleBuilder.AddUrlAction(action);
 
             var options = new RewriteOptions().Add(ruleBuilder.Build());
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                         app.Run(context => context.Response.WriteAsync(context.Request.GetEncodedUrl()));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             // act
             var response = await server.CreateClient().GetStringAsync("http://localhost/foo/bar");

src/Middleware/Rewrite/test/MiddlewareTests.cs

@@ -8,6 +8,7 @@ using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
@@ -18,7 +19,11 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckRewritePath()
         {
             var options = new RewriteOptions().AddRewrite("(.*)", "http://example.com/$1", skipRemainingRules: false);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
@@ -29,7 +34,11 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
                             context.Request.Path +
                             context.Request.QueryString));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync("foo");
 
@@ -40,12 +49,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckRedirectPath()
         {
             var options = new RewriteOptions().AddRedirect("(.*)", "http://example.com/$1", statusCode: StatusCodes.Status301MovedPermanently);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync("foo");
 
@@ -55,7 +72,11 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         [Fact]
         public async Task RewriteRulesCanComeFromConfigureOptions()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .ConfigureServices(services =>
                     {
                         services.Configure<RewriteOptions>(options =>
@@ -67,7 +88,11 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
                     {
                         app.UseRewriter();
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync("foo");
 
@@ -78,12 +103,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckRedirectPathWithQueryString()
         {
             var options = new RewriteOptions().AddRedirect("(.*)", "http://example.com/$1", statusCode: StatusCodes.Status301MovedPermanently);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync("foo?bar=1");
 
@@ -98,12 +131,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckRedirectToHttps(int statusCode)
         {
             var options = new RewriteOptions().AddRedirectToHttps(statusCode: statusCode);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync(new Uri("http://example.com"));
 
@@ -115,12 +156,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckPermanentRedirectToHttps()
         {
             var options = new RewriteOptions().AddRedirectToHttpsPermanent();
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync(new Uri("http://example.com"));
 
@@ -134,12 +183,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckRedirectToHttpsWithSslPort(int sslPort, string expected)
         {
             var options = new RewriteOptions().AddRedirectToHttps(statusCode: StatusCodes.Status301MovedPermanently, sslPort: sslPort);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync(new Uri("http://example.com"));
 
@@ -155,12 +212,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckRedirectToWwwWithStatusCode(int statusCode)
         {
             var options = new RewriteOptions().AddRedirectToWww(statusCode: statusCode);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync(new Uri("https://example.com"));
 
@@ -176,12 +241,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckRedirectToWww(string requestUri, string redirectUri)
         {
             var options = new RewriteOptions().AddRedirectToWww();
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync(new Uri(requestUri));
 
@@ -193,12 +266,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckPermanentRedirectToWww()
         {
             var options = new RewriteOptions().AddRedirectToWwwPermanent();
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync(new Uri("https://example.com"));
 
@@ -220,12 +301,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckNoRedirectToWww(string requestUri)
         {
             var options = new RewriteOptions().AddRedirectToWww();
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync(new Uri(requestUri));
 
@@ -240,12 +329,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckRedirectToNonWwwWithStatusCode(int statusCode)
         {
             var options = new RewriteOptions().AddRedirectToNonWww(statusCode: statusCode);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync(new Uri("https://www.example.com"));
 
@@ -261,12 +358,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckRedirectToNonWww(string requestUri, string redirectUri)
         {
             var options = new RewriteOptions().AddRedirectToNonWww();
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync(new Uri(requestUri));
 
@@ -278,12 +383,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckPermanentRedirectToNonWww()
         {
             var options = new RewriteOptions().AddRedirectToNonWwwPermanent();
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync(new Uri("https://www.example.com"));
 
@@ -295,12 +408,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckIfEmptyStringRedirectCorrectly()
         {
             var options = new RewriteOptions().AddRedirect("(.*)", "$1", statusCode: StatusCodes.Status301MovedPermanently);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync("");
             Assert.Equal("/", response.Headers.Location.OriginalString);
@@ -310,7 +431,11 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckIfEmptyStringRewriteCorrectly()
         {
             var options = new RewriteOptions().AddRewrite("(.*)", "$1", skipRemainingRules: false);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
@@ -318,7 +443,11 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
                                 context.Request.Path +
                                 context.Request.QueryString));
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetStringAsync("");
 
@@ -329,7 +458,11 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task SettingPathBase()
         {
             var options = new RewriteOptions().AddRedirect("(.*)", "$1");
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
@@ -337,7 +470,12 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
                                 context.Request.Path +
                                 context.Request.QueryString));
                     });
-            var server = new TestServer(builder) { BaseAddress = new Uri("http://localhost:5000/foo") };
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
+            server.BaseAddress = new Uri("http://localhost:5000/foo");
 
             var response = await server.CreateClient().GetAsync("");
 
@@ -353,12 +491,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckNoRedirectToWwwInNonWhitelistedDomains(string requestUri)
         {
             var options = new RewriteOptions().AddRedirectToWww("example2.com");
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync(new Uri(requestUri));
 
@@ -373,12 +519,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckRedirectToWwwInWhitelistedDomains(string requestUri, string redirectUri)
         {
             var options = new RewriteOptions().AddRedirectToWww("example.com");
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync(new Uri(requestUri));
 
@@ -390,12 +544,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckPermanentRedirectToWwwInWhitelistedDomains()
         {
             var options = new RewriteOptions().AddRedirectToWwwPermanent("example.com");
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync(new Uri("https://example.com"));
 
@@ -411,12 +573,20 @@ namespace Microsoft.AspNetCore.Rewrite.Tests.CodeRules
         public async Task CheckRedirectToWwwWithStatusCodeInWhitelistedDomains(int statusCode)
         {
             var options = new RewriteOptions().AddRedirectToWww(statusCode: statusCode, "example.com");
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseRewriter(options);
                     });
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync(new Uri("https://example.com"));
 

src/Middleware/Session/samples/Startup.cs

@@ -2,10 +2,12 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 
 namespace SessionSample
@@ -81,16 +83,19 @@ namespace SessionSample
             });
         }
 
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .ConfigureLogging(factory => factory.AddConsole())
                     .UseKestrel()
                     .UseIISIntegration()
-                .UseStartup<Startup>()
-                .Build();
+                    .UseStartup<Startup>();
+                }).Build();
 
-            host.Run();
+            return host.RunAsync();
         }
     }
 }

src/Middleware/Session/test/SessionTests.cs

@@ -14,6 +14,7 @@ using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.Caching.Distributed;
 using Microsoft.Extensions.Caching.Memory;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Internal;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Logging.Abstractions;
@@ -29,7 +30,11 @@ namespace Microsoft.AspNetCore.Session
         [Fact]
         public async Task ReadingEmptySessionDoesNotCreateCookie()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession();
@@ -45,8 +50,11 @@ namespace Microsoft.AspNetCore.Session
                         services.AddDistributedMemoryCache();
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -58,7 +66,11 @@ namespace Microsoft.AspNetCore.Session
         [Fact]
         public async Task SettingAValueCausesTheCookieToBeCreated()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession();
@@ -75,8 +87,11 @@ namespace Microsoft.AspNetCore.Session
                         services.AddDistributedMemoryCache();
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -99,7 +114,11 @@ namespace Microsoft.AspNetCore.Session
             string requestUri,
             bool shouldBeSecureOnly)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession(new SessionOptions
@@ -123,8 +142,11 @@ namespace Microsoft.AspNetCore.Session
                         services.AddDistributedMemoryCache();
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(requestUri);
@@ -145,7 +167,11 @@ namespace Microsoft.AspNetCore.Session
         [Fact]
         public async Task SessionCanBeAccessedOnTheNextRequest()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession();
@@ -167,8 +193,11 @@ namespace Microsoft.AspNetCore.Session
                         services.AddDistributedMemoryCache();
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync("first");
@@ -187,7 +216,11 @@ namespace Microsoft.AspNetCore.Session
         [Fact]
         public async Task RemovedItemCannotBeAccessedAgain()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession();
@@ -220,8 +253,11 @@ namespace Microsoft.AspNetCore.Session
                         services.AddDistributedMemoryCache();
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync("first");
@@ -239,7 +275,11 @@ namespace Microsoft.AspNetCore.Session
         [Fact]
         public async Task ClearedItemsCannotBeAccessedAgain()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession();
@@ -271,8 +311,11 @@ namespace Microsoft.AspNetCore.Session
                         services.AddDistributedMemoryCache();
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync("first");
@@ -294,7 +337,11 @@ namespace Microsoft.AspNetCore.Session
                 TestSink.EnableWithTypeName<DistributedSession>,
                 TestSink.EnableWithTypeName<DistributedSession>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession();
@@ -310,8 +357,11 @@ namespace Microsoft.AspNetCore.Session
                         services.AddDistributedMemoryCache();
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -334,7 +384,11 @@ namespace Microsoft.AspNetCore.Session
                 TestSink.EnableWithTypeName<DistributedSession>,
                 TestSink.EnableWithTypeName<DistributedSession>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession();
@@ -361,9 +415,12 @@ namespace Microsoft.AspNetCore.Session
                         services.AddDistributedMemoryCache();
                         services.AddSession(o => o.IdleTimeout = TimeSpan.FromMilliseconds(30));
                     });
+                }).Build();
+
+            await host.StartAsync();
 
             string result;
-            using (var server = new TestServer(builder))
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync("first");
@@ -392,7 +449,11 @@ namespace Microsoft.AspNetCore.Session
         public async Task RefreshesSession_WhenSessionData_IsNotModified()
         {
             var clock = new TestClock();
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession();
@@ -424,8 +485,11 @@ namespace Microsoft.AspNetCore.Session
                         services.AddSession(o => o.IdleTimeout = TimeSpan.FromMinutes(20));
                         services.Configure<MemoryCacheOptions>(o => o.Clock = clock);
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync("AddDataToSession");
@@ -450,7 +514,11 @@ namespace Microsoft.AspNetCore.Session
         [Fact]
         public async Task SessionFeature_IsUnregistered_WhenResponseGoingOut()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.Use(async (httpContext, next) =>
@@ -473,8 +541,11 @@ namespace Microsoft.AspNetCore.Session
                         services.AddDistributedMemoryCache();
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -485,7 +556,11 @@ namespace Microsoft.AspNetCore.Session
         [Fact]
         public async Task SessionFeature_IsUnregistered_WhenResponseGoingOut_AndAnUnhandledExcetionIsThrown()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.Use(async (httpContext, next) =>
@@ -516,8 +591,11 @@ namespace Microsoft.AspNetCore.Session
                         services.AddDistributedMemoryCache();
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -527,7 +605,11 @@ namespace Microsoft.AspNetCore.Session
         [Fact]
         public async Task SessionKeys_AreCaseSensitive()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession();
@@ -545,8 +627,11 @@ namespace Microsoft.AspNetCore.Session
                         services.AddDistributedMemoryCache();
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -561,7 +646,11 @@ namespace Microsoft.AspNetCore.Session
                 TestSink.EnableWithTypeName<DistributedSession>,
                 TestSink.EnableWithTypeName<DistributedSession>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession();
@@ -583,8 +672,11 @@ namespace Microsoft.AspNetCore.Session
                         });
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -603,7 +695,11 @@ namespace Microsoft.AspNetCore.Session
                 TestSink.EnableWithTypeName<DistributedSession>,
                 TestSink.EnableWithTypeName<DistributedSession>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession();
@@ -624,8 +720,11 @@ namespace Microsoft.AspNetCore.Session
                         });
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -644,7 +743,11 @@ namespace Microsoft.AspNetCore.Session
                 TestSink.EnableWithTypeName<DistributedSession>,
                 TestSink.EnableWithTypeName<DistributedSession>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession(new SessionOptions()
@@ -665,8 +768,11 @@ namespace Microsoft.AspNetCore.Session
                         });
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -685,7 +791,11 @@ namespace Microsoft.AspNetCore.Session
                 TestSink.EnableWithTypeName<DistributedSession>,
                 TestSink.EnableWithTypeName<DistributedSession>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession();
@@ -706,8 +816,11 @@ namespace Microsoft.AspNetCore.Session
                         });
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -732,7 +845,11 @@ namespace Microsoft.AspNetCore.Session
                         || beginScopeContext.LoggerName.Equals(typeof(DistributedSession).FullName);
                 });
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession();
@@ -751,8 +868,11 @@ namespace Microsoft.AspNetCore.Session
                         });
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -785,7 +905,11 @@ namespace Microsoft.AspNetCore.Session
                         || beginScopeContext.LoggerName.Equals(typeof(DistributedSession).FullName);
                 });
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession(new SessionOptions()
@@ -807,8 +931,11 @@ namespace Microsoft.AspNetCore.Session
                         });
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -844,7 +971,11 @@ namespace Microsoft.AspNetCore.Session
                         || beginScopeContext.LoggerName.Equals(typeof(DistributedSession).FullName);
                 });
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession();
@@ -866,8 +997,11 @@ namespace Microsoft.AspNetCore.Session
                         });
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -901,7 +1035,11 @@ namespace Microsoft.AspNetCore.Session
                         || beginScopeContext.LoggerName.Equals(typeof(DistributedSession).FullName);
                 });
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession();
@@ -924,8 +1062,11 @@ namespace Microsoft.AspNetCore.Session
                         });
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);
@@ -950,7 +1091,11 @@ namespace Microsoft.AspNetCore.Session
                 TestSink.EnableWithTypeName<SessionMiddleware>,
                 TestSink.EnableWithTypeName<SessionMiddleware>);
             var loggerFactory = new TestLoggerFactory(sink, enabled: true);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.UseSession();
@@ -969,8 +1114,11 @@ namespace Microsoft.AspNetCore.Session
                         });
                         services.AddSession();
                     });
+                }).Build();
 
-            using (var server = new TestServer(builder))
+            await host.StartAsync();
+
+            using (var server = host.GetTestServer())
             {
                 var client = server.CreateClient();
                 var response = await client.GetAsync(string.Empty);

src/Middleware/StaticFiles/samples/StaticFileSample/Startup.cs

@@ -1,8 +1,10 @@
 using System;
 using System.IO;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 
 namespace StaticFilesSample
@@ -25,9 +27,12 @@ namespace StaticFilesSample
             });
         }
 
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .ConfigureLogging(factory =>
                     {
                         factory.AddFilter("Console", level => level >= LogLevel.Debug);
@@ -37,10 +42,10 @@ namespace StaticFilesSample
                     .UseKestrel()
                     // .UseHttpSys()
                     .UseIISIntegration()
-                .UseStartup<Startup>()
-                .Build();
+                    .UseStartup<Startup>();
+                }).Build();
 
-            host.Run();
+            return host.RunAsync();
         }
     }
 }

src/Middleware/StaticFiles/test/FunctionalTests/FallbackStaticFileTest.cs

@@ -15,6 +15,7 @@ using Microsoft.AspNetCore.Server.IntegrationTesting.Common;
 using Microsoft.AspNetCore.Testing;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.FileProviders;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging.Testing;
 using Xunit;
 
@@ -25,13 +26,17 @@ namespace Microsoft.AspNetCore.StaticFiles
         [Fact]
         public async Task ReturnsFileForDefaultPattern()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .ConfigureServices(services =>
                     {
                         services.AddRouting();
                         services.AddSingleton(LoggerFactory);
                     })
                     .UseKestrel()
+                    .UseUrls(TestUrlHelper.GetTestUrl(ServerType.Kestrel))
                     .UseWebRoot(AppContext.BaseDirectory)
                     .Configure(app =>
                     {
@@ -50,11 +55,12 @@ namespace Microsoft.AspNetCore.StaticFiles
                             });
                         });
                     });
+                }).Build();
 
-            using (var server = builder.Start(TestUrlHelper.GetTestUrl(ServerType.Kestrel)))
-            {
-                var environment = server.Services.GetRequiredService<IWebHostEnvironment>();
-                using (var client = new HttpClient { BaseAddress = new Uri(Helpers.GetAddress(server)) })
+            await host.StartAsync();
+
+            var environment = host.Services.GetRequiredService<IWebHostEnvironment>();
+            using (var client = new HttpClient { BaseAddress = new Uri(Helpers.GetAddress(host)) })
             {
                 var response = await client.GetAsync("hello");
                 var responseText = await response.Content.ReadAsStringAsync();
@@ -69,18 +75,21 @@ namespace Microsoft.AspNetCore.StaticFiles
                 AssertFileEquals(environment, "SubFolder/default.html", responseContent);
             }
         }
-        }
 
         [Fact]
         public async Task ReturnsFileForCustomPattern()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .ConfigureServices(services =>
                     {
                         services.AddRouting();
                         services.AddSingleton(LoggerFactory);
                     })
                     .UseKestrel()
+                    .UseUrls(TestUrlHelper.GetTestUrl(ServerType.Kestrel))
                     .UseWebRoot(AppContext.BaseDirectory)
                     .Configure(app =>
                     {
@@ -95,11 +104,12 @@ namespace Microsoft.AspNetCore.StaticFiles
                             endpoints.MapFallbackToFile("/prefix/{*path:nonfile}", "TestDocument.txt");
                         });
                     });
+                }).Build();
 
-            using (var server = builder.Start(TestUrlHelper.GetTestUrl(ServerType.Kestrel)))
-            {
-                var environment = server.Services.GetRequiredService<IWebHostEnvironment>();
-                using (var client = new HttpClient { BaseAddress = new Uri(Helpers.GetAddress(server)) })
+            await host.StartAsync();
+
+            var environment = host.Services.GetRequiredService<IWebHostEnvironment>();
+            using (var client = new HttpClient { BaseAddress = new Uri(Helpers.GetAddress(host)) })
             {
                 var response = await client.GetAsync("hello");
                 var responseText = await response.Content.ReadAsStringAsync();
@@ -114,7 +124,6 @@ namespace Microsoft.AspNetCore.StaticFiles
                 AssertFileEquals(environment, "TestDocument.txt", responseContent);
             }
         }
-        }
 
         private static void AssertFileEquals(IWebHostEnvironment environment, string filePath, byte[] responseContent)
         {

src/Middleware/StaticFiles/test/FunctionalTests/Helpers.cs

@@ -3,15 +3,18 @@
 
 using System.Linq;
 using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Hosting.Server;
 using Microsoft.AspNetCore.Hosting.Server.Features;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 
 namespace Microsoft.AspNetCore.StaticFiles
 {
     public static class Helpers
     {
-        public static string GetAddress(IWebHost server)
+        public static string GetAddress(IHost server)
         {
-            return server.ServerFeatures.Get<IServerAddressesFeature>().Addresses.First();
+            return server.Services.GetService<IServer>().Features.Get<IServerAddressesFeature>().Addresses.First();
         }
     }
 }

src/Middleware/StaticFiles/test/FunctionalTests/StaticFileMiddlewareTests.cs

@@ -18,6 +18,7 @@ using Microsoft.AspNetCore.Server.IntegrationTesting;
 using Microsoft.AspNetCore.Server.IntegrationTesting.Common;
 using Microsoft.AspNetCore.Testing;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging.Testing;
 using Xunit;
 
@@ -28,28 +29,36 @@ namespace Microsoft.AspNetCore.StaticFiles
         [Fact]
         public async Task ReturnsNotFoundWithoutWwwroot()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .ConfigureServices(services => services.AddSingleton(LoggerFactory))
                     .UseKestrel()
+                    .UseUrls(TestUrlHelper.GetTestUrl(ServerType.Kestrel))
                     .Configure(app => app.UseStaticFiles());
+                }).Build();
 
-            using (var server = builder.Start(TestUrlHelper.GetTestUrl(ServerType.Kestrel)))
-            {
-                using (var client = new HttpClient { BaseAddress = new Uri(Helpers.GetAddress(server)) })
+            await host.StartAsync();
+
+            using (var client = new HttpClient { BaseAddress = new Uri(Helpers.GetAddress(host)) })
             {
                 var response = await client.GetAsync("TestDocument.txt");
 
                 Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
             }
         }
-        }
 
         [Fact]
         public async Task Endpoint_PassesThrough()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .ConfigureServices(services => { services.AddSingleton(LoggerFactory); services.AddRouting(); })
                     .UseKestrel()
+                    .UseUrls(TestUrlHelper.GetTestUrl(ServerType.Kestrel))
                     .UseWebRoot(AppContext.BaseDirectory)
                     .Configure(app =>
                     {
@@ -71,12 +80,13 @@ namespace Microsoft.AspNetCore.StaticFiles
 
                         app.UseStaticFiles();
 
-                    app.UseEndpoints(endpoints => {});
+                        app.UseEndpoints(endpoints => { });
                     });
+                }).Build();
 
-            using (var server = builder.Start(TestUrlHelper.GetTestUrl(ServerType.Kestrel)))
-            {
-                using (var client = new HttpClient { BaseAddress = new Uri(Helpers.GetAddress(server)) })
+            await host.StartAsync();
+
+            using (var client = new HttpClient { BaseAddress = new Uri(Helpers.GetAddress(host)) })
             {
                 var response = await client.GetAsync("TestDocument.txt");
 
@@ -84,20 +94,24 @@ namespace Microsoft.AspNetCore.StaticFiles
                 Assert.Equal("Hi from endpoint.", await response.Content.ReadAsStringAsync());
             }
         }
-        }
 
         [Fact]
         public async Task FoundFile_LastModifiedTrimsSeconds()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .ConfigureServices(services => services.AddSingleton(LoggerFactory))
                     .UseKestrel()
+                    .UseUrls(TestUrlHelper.GetTestUrl(ServerType.Kestrel))
                     .UseWebRoot(AppContext.BaseDirectory)
                     .Configure(app => app.UseStaticFiles());
+                }).Build();
 
-            using (var server = builder.Start(TestUrlHelper.GetTestUrl(ServerType.Kestrel)))
-            {
-                using (var client = new HttpClient { BaseAddress = new Uri(Helpers.GetAddress(server)) })
+            await host.StartAsync();
+
+            using (var client = new HttpClient { BaseAddress = new Uri(Helpers.GetAddress(host)) })
             {
                 var last = File.GetLastWriteTimeUtc(Path.Combine(AppContext.BaseDirectory, "TestDocument.txt"));
                 var response = await client.GetAsync("TestDocument.txt");
@@ -107,7 +121,6 @@ namespace Microsoft.AspNetCore.StaticFiles
                 Assert.Equal(response.Content.Headers.LastModified.Value, trimmed);
             }
         }
-        }
 
         [Theory]
         [MemberData(nameof(ExistingFiles))]
@@ -130,20 +143,25 @@ namespace Microsoft.AspNetCore.StaticFiles
 
         private async Task FoundFile_Served(string baseUrl, string baseDir, string requestUrl)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .ConfigureServices(services => services.AddSingleton(LoggerFactory))
                     .UseKestrel()
+                    .UseUrls(TestUrlHelper.GetTestUrl(ServerType.Kestrel))
                     .UseWebRoot(Path.Combine(AppContext.BaseDirectory, baseDir))
                     .Configure(app => app.UseStaticFiles(new StaticFileOptions
                     {
                         RequestPath = new PathString(baseUrl),
                     }));
+                }).Build();
 
-            using (var server = builder.Start(TestUrlHelper.GetTestUrl(ServerType.Kestrel)))
-            {
-                var hostingEnvironment = server.Services.GetService<IWebHostEnvironment>();
+            await host.StartAsync();
 
-                using (var client = new HttpClient { BaseAddress = new Uri(Helpers.GetAddress(server)) })
+            var hostingEnvironment = host.Services.GetService<IWebHostEnvironment>();
+
+            using (var client = new HttpClient { BaseAddress = new Uri(Helpers.GetAddress(host)) })
             {
                 var fileInfo = hostingEnvironment.WebRootFileProvider.GetFileInfo(Path.GetFileName(requestUrl));
                 var response = await client.GetAsync(requestUrl);
@@ -162,13 +180,15 @@ namespace Microsoft.AspNetCore.StaticFiles
                 }
             }
         }
-        }
 
         [Theory]
         [MemberData(nameof(ExistingFiles))]
         public async Task HeadFile_HeadersButNotBodyServed(string baseUrl, string baseDir, string requestUrl)
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .ConfigureServices(services => services.AddSingleton(LoggerFactory))
                     .UseKestrel()
                     .UseWebRoot(Path.Combine(AppContext.BaseDirectory, baseDir))
@@ -176,12 +196,13 @@ namespace Microsoft.AspNetCore.StaticFiles
                     {
                         RequestPath = new PathString(baseUrl),
                     }));
+                }).Build();
 
-            using (var server = builder.Start(TestUrlHelper.GetTestUrl(ServerType.Kestrel)))
-            {
-                var hostingEnvironment = server.Services.GetService<IWebHostEnvironment>();
+            await host.StartAsync();
 
-                using (var client = new HttpClient { BaseAddress = new Uri(Helpers.GetAddress(server)) })
+            var hostingEnvironment = host.Services.GetService<IWebHostEnvironment>();
+
+            using (var client = new HttpClient { BaseAddress = new Uri(Helpers.GetAddress(host)) })
             {
                 var fileInfo = hostingEnvironment.WebRootFileProvider.GetFileInfo(Path.GetFileName(requestUrl));
                 var request = new HttpRequestMessage(HttpMethod.Head, requestUrl);
@@ -193,7 +214,6 @@ namespace Microsoft.AspNetCore.StaticFiles
                 Assert.Empty((await response.Content.ReadAsByteArrayAsync()));
             }
         }
-        }
 
         public static IEnumerable<object[]> ExistingFiles => new[]
         {
@@ -226,7 +246,10 @@ namespace Microsoft.AspNetCore.StaticFiles
             var requestCancelled = new TaskCompletionSource<int>(TaskCreationOptions.RunContinuationsAsynchronously);
             var responseComplete = new TaskCompletionSource<int>(TaskCreationOptions.RunContinuationsAsynchronously);
             Exception exception = null;
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .ConfigureServices(services => services.AddSingleton(LoggerFactory))
                     .UseWebRoot(Path.Combine(AppContext.BaseDirectory))
                     .Configure(app =>
@@ -247,21 +270,23 @@ namespace Microsoft.AspNetCore.StaticFiles
                             responseComplete.SetResult(0);
                         });
                         app.UseStaticFiles();
-                });
+                    })
+                    .UseUrls(TestUrlHelper.GetTestUrl(serverType));
 
                     if (serverType == ServerType.HttpSys)
                     {
-                builder.UseHttpSys();
+                        webHostBuilder.UseHttpSys();
                     }
                     else if (serverType == ServerType.Kestrel)
                     {
-                builder.UseKestrel();
+                        webHostBuilder.UseKestrel();
                     }
+                }).Build();
+
+            await host.StartAsync();
 
-            using (var server = builder.Start(TestUrlHelper.GetTestUrl(serverType)))
-            {
             // We don't use HttpClient here because it's disconnect behavior varies across platforms.
-                var socket = SendSocketRequestAsync(Helpers.GetAddress(server), "/TestDocument1MB.txt");
+            var socket = SendSocketRequestAsync(Helpers.GetAddress(host), "/TestDocument1MB.txt");
             await requestReceived.Task.TimeoutAfter(interval);
 
             socket.LingerState = new LingerOption(true, 0);
@@ -271,7 +296,6 @@ namespace Microsoft.AspNetCore.StaticFiles
             await responseComplete.Task.TimeoutAfter(interval);
             Assert.Null(exception);
         }
-        }
 
         private Socket SendSocketRequestAsync(string address, string path, string method = "GET")
         {

src/Middleware/StaticFiles/test/UnitTests/CacheHeaderTests.cs

@@ -18,7 +18,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [Fact]
         public async Task ServerShouldReturnETag()
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
 
             HttpResponseMessage response = await server.CreateClient().GetAsync("http://localhost/SubFolder/extra.xml");
             Assert.NotNull(response.Headers.ETag);
@@ -28,7 +29,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [Fact]
         public async Task SameETagShouldBeReturnedAgain()
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
 
             HttpResponseMessage response1 = await server.CreateClient().GetAsync("http://localhost/SubFolder/extra.xml");
             HttpResponseMessage response2 = await server.CreateClient().GetAsync("http://localhost/SubFolder/extra.xml");
@@ -47,7 +49,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(SupportedMethods))]
         public async Task IfMatchShouldReturn412WhenNotListed(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             var req = new HttpRequestMessage(method, "http://localhost/SubFolder/extra.xml");
             req.Headers.Add("If-Match", "\"fake\"");
             HttpResponseMessage resp = await server.CreateClient().SendAsync(req);
@@ -58,7 +61,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(SupportedMethods))]
         public async Task IfMatchShouldBeServedWhenListed(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             HttpResponseMessage original = await server.CreateClient().GetAsync("http://localhost/SubFolder/extra.xml");
 
             var req = new HttpRequestMessage(method, "http://localhost/SubFolder/extra.xml");
@@ -71,7 +75,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(SupportedMethods))]
         public async Task IfMatchShouldBeServedForAsterisk(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             var req = new HttpRequestMessage(method, "http://localhost/SubFolder/extra.xml");
             req.Headers.Add("If-Match", "*");
             HttpResponseMessage resp = await server.CreateClient().SendAsync(req);
@@ -82,7 +87,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(UnsupportedMethods))]
         public async Task IfMatchShouldBeIgnoredForUnsupportedMethods(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             var req = new HttpRequestMessage(method, "http://localhost/SubFolder/extra.xml");
             req.Headers.Add("If-Match", "*");
             HttpResponseMessage resp = await server.CreateClient().SendAsync(req);
@@ -107,7 +113,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(SupportedMethods))]
         public async Task IfNoneMatchShouldReturn304ForMatching(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             HttpResponseMessage resp1 = await server.CreateClient().GetAsync("http://localhost/SubFolder/extra.xml");
 
             var req2 = new HttpRequestMessage(method, "http://localhost/SubFolder/extra.xml");
@@ -120,7 +127,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(SupportedMethods))]
         public async Task IfNoneMatchAllShouldReturn304ForMatching(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             HttpResponseMessage resp1 = await server.CreateClient().GetAsync("http://localhost/SubFolder/extra.xml");
 
             var req2 = new HttpRequestMessage(method, "http://localhost/SubFolder/extra.xml");
@@ -133,7 +141,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(UnsupportedMethods))]
         public async Task IfNoneMatchShouldBeIgnoredForNonTwoHundredAnd304Responses(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             HttpResponseMessage resp1 = await server.CreateClient().GetAsync("http://localhost/SubFolder/extra.xml");
 
             var req2 = new HttpRequestMessage(method, "http://localhost/SubFolder/extra.xml");
@@ -156,7 +165,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(SupportedMethods))]
         public async Task ServerShouldReturnLastModified(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
 
             HttpResponseMessage response = await server.CreateClient().SendAsync(
                 new HttpRequestMessage(method, "http://localhost/SubFolder/extra.xml"));
@@ -179,7 +189,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(SupportedMethods))]
         public async Task MatchingBothConditionsReturnsNotModified(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             HttpResponseMessage resp1 = await server
                 .CreateRequest("/SubFolder/extra.xml")
                 .SendAsync(method.Method);
@@ -198,7 +209,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(SupportedMethods))]
         public async Task MatchingAtLeastOneETagReturnsNotModified(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             HttpResponseMessage resp1 = await server
                 .CreateRequest("/SubFolder/extra.xml")
                 .SendAsync(method.Method);
@@ -223,7 +235,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(SupportedMethods))]
         public async Task MissingEitherOrBothConditionsReturnsNormally(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             HttpResponseMessage resp1 = await server
                 .CreateRequest("/SubFolder/extra.xml")
                 .SendAsync(method.Method);
@@ -271,7 +284,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(SupportedMethods))]
         public async Task InvalidIfModifiedSinceDateFormatGivesNormalGet(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
 
             HttpResponseMessage res = await server
                 .CreateRequest("/SubFolder/extra.xml")
@@ -285,7 +299,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(SupportedMethods))]
         public async Task FutureIfModifiedSinceDateFormatGivesNormalGet(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
 
             HttpResponseMessage res = await server
                 .CreateRequest("/SubFolder/extra.xml")
@@ -306,7 +321,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(SupportedMethods))]
         public async Task IfModifiedSinceDateGreaterThanLastModifiedShouldReturn304(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
 
             HttpResponseMessage res1 = await server
                 .CreateRequest("/SubFolder/extra.xml")
@@ -324,7 +340,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(SupportedMethods))]
         public async Task SupportsIfModifiedDateFormats(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             HttpResponseMessage res1 = await server
                 .CreateRequest("/SubFolder/extra.xml")
                 .SendAsync(method.Method);
@@ -351,7 +368,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(SupportedMethods))]
         public async Task IfModifiedSinceDateLessThanLastModifiedShouldReturn200(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
 
             HttpResponseMessage res1 = await server
                 .CreateRequest("/SubFolder/extra.xml")
@@ -369,7 +387,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(SupportedMethods))]
         public async Task InvalidIfUnmodifiedSinceDateFormatGivesNormalGet(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
 
             HttpResponseMessage res = await server
                 .CreateRequest("/SubFolder/extra.xml")
@@ -383,7 +402,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(SupportedMethods))]
         public async Task FutureIfUnmodifiedSinceDateFormatGivesNormalGet(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
 
             HttpResponseMessage res = await server
                 .CreateRequest("/SubFolder/extra.xml")
@@ -397,7 +417,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [MemberData(nameof(SupportedMethods))]
         public async Task IfUnmodifiedSinceDateLessThanLastModifiedShouldReturn412(HttpMethod method)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
 
             HttpResponseMessage res1 = await server
                 .CreateRequest("/SubFolder/extra.xml")

src/Middleware/StaticFiles/test/UnitTests/DefaultFilesMiddlewareTests.cs

@@ -24,10 +24,12 @@ namespace Microsoft.AspNetCore.StaticFiles
         public async Task NullArguments()
         {
             // No exception, default provided
-            StaticFilesTestServer.Create(app => app.UseDefaultFiles(new DefaultFilesOptions { FileProvider = null }));
+            using (await StaticFilesTestServer.Create(app => app.UseDefaultFiles(new DefaultFilesOptions { FileProvider = null })))
+            { }
 
             // PathString(null) is OK.
-            var server = StaticFilesTestServer.Create(app => app.UseDefaultFiles((string)null));
+            using var host = await StaticFilesTestServer.Create(app => app.UseDefaultFiles((string)null));
+            using var server = host.GetTestServer();
             var response = await server.CreateClient().GetAsync("/");
             Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
         }
@@ -64,7 +66,7 @@ namespace Microsoft.AspNetCore.StaticFiles
         {
             using (var fileProvider = new PhysicalFileProvider(Path.Combine(AppContext.BaseDirectory, baseDir)))
             {
-                var server = StaticFilesTestServer.Create(app =>
+                using var host = await StaticFilesTestServer.Create(app =>
                 {
                     app.UseDefaultFiles(new DefaultFilesOptions
                     {
@@ -74,6 +76,7 @@ namespace Microsoft.AspNetCore.StaticFiles
                     });
                     app.Run(context => context.Response.WriteAsync(context.Request.Path.Value));
                 });
+                using var server = host.GetTestServer();
 
                 var response = await server.CreateClient().GetAsync(requestUrl);
                 Assert.Equal(HttpStatusCode.OK, response.StatusCode);
@@ -86,7 +89,7 @@ namespace Microsoft.AspNetCore.StaticFiles
         {
             using (var fileProvider = new PhysicalFileProvider(Path.Combine(AppContext.BaseDirectory, ".")))
             {
-                var server = StaticFilesTestServer.Create(
+                using var host = await StaticFilesTestServer.Create(
                     app =>
                     {
                         app.UseRouting();
@@ -113,6 +116,7 @@ namespace Microsoft.AspNetCore.StaticFiles
                         app.UseEndpoints(endpoints => { });
                     },
                     services => { services.AddDirectoryBrowser(); services.AddRouting(); });
+                using var server = host.GetTestServer();
 
                 var response = await server.CreateRequest("/SubFolder/").GetAsync();
                 Assert.Equal(HttpStatusCode.OK, response.StatusCode);
@@ -165,7 +169,7 @@ namespace Microsoft.AspNetCore.StaticFiles
         {
             using (var fileProvider = new PhysicalFileProvider(Path.Combine(AppContext.BaseDirectory, baseDir)))
             {
-                var server = StaticFilesTestServer.Create(app =>
+                using var host = await StaticFilesTestServer.Create(app =>
                 {
                     app.UseDefaultFiles(new DefaultFilesOptions
                     {
@@ -175,6 +179,7 @@ namespace Microsoft.AspNetCore.StaticFiles
                     });
                     app.Run(context => context.Response.WriteAsync(context.Request.Path.Value));
                 });
+                using var server = host.GetTestServer();
 
                 var response = await server.CreateClient().GetAsync(requestUrl);
 
@@ -211,11 +216,12 @@ namespace Microsoft.AspNetCore.StaticFiles
         {
             using (var fileProvider = new PhysicalFileProvider(Path.Combine(AppContext.BaseDirectory, baseDir)))
             {
-                var server = StaticFilesTestServer.Create(app => app.UseDefaultFiles(new DefaultFilesOptions
+                using var host = await StaticFilesTestServer.Create(app => app.UseDefaultFiles(new DefaultFilesOptions
                 {
                     RequestPath = new PathString(baseUrl),
                     FileProvider = fileProvider
                 }));
+                using var server = host.GetTestServer();
                 var response = await server.CreateRequest(requestUrl + queryString).GetAsync();
 
                 Assert.Equal(HttpStatusCode.Moved, response.StatusCode);
@@ -265,12 +271,13 @@ namespace Microsoft.AspNetCore.StaticFiles
         {
             using (var fileProvider = new PhysicalFileProvider(Path.Combine(AppContext.BaseDirectory, baseDir)))
             {
-                var server = StaticFilesTestServer.Create(app => app.UseDefaultFiles(new DefaultFilesOptions
+                using var host = await StaticFilesTestServer.Create(app => app.UseDefaultFiles(new DefaultFilesOptions
                 {
                     RequestPath = new PathString(baseUrl),
                     FileProvider = fileProvider,
                     RedirectToAppendTrailingSlash = appendTrailingSlash
                 }));
+                using var server = host.GetTestServer();
                 var response = await server.CreateRequest(requestUrl).GetAsync();
 
                 Assert.Equal(HttpStatusCode.NotFound, response.StatusCode); // Passed through

src/Middleware/StaticFiles/test/UnitTests/DirectoryBrowserMiddlewareTests.cs

@@ -21,10 +21,10 @@ namespace Microsoft.AspNetCore.StaticFiles
     public class DirectoryBrowserMiddlewareTests
     {
         [Fact]
-        public void WorksWithoutEncoderRegistered()
+        public async Task WorksWithoutEncoderRegistered()
         {
             // No exception, uses HtmlEncoder.Default
-            StaticFilesTestServer.Create(
+            using var host = await StaticFilesTestServer.Create(
                 app => app.UseDirectoryBrowser());
         }
 
@@ -32,19 +32,24 @@ namespace Microsoft.AspNetCore.StaticFiles
         public async Task NullArguments()
         {
             // No exception, default provided
-            StaticFilesTestServer.Create(
+            using (await StaticFilesTestServer.Create(
                 app => app.UseDirectoryBrowser(new DirectoryBrowserOptions { Formatter = null }),
-            services => services.AddDirectoryBrowser());
+                services => services.AddDirectoryBrowser()))
+            {
+            }
 
             // No exception, default provided
-            StaticFilesTestServer.Create(
+            using (await StaticFilesTestServer.Create(
                 app => app.UseDirectoryBrowser(new DirectoryBrowserOptions { FileProvider = null }),
-                services => services.AddDirectoryBrowser());
+                services => services.AddDirectoryBrowser()))
+            {
+            }
 
             // PathString(null) is OK.
-            var server = StaticFilesTestServer.Create(
+            using var host = await StaticFilesTestServer.Create(
                 app => app.UseDirectoryBrowser((string)null),
                 services => services.AddDirectoryBrowser());
+            using var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync("/");
             Assert.Equal(HttpStatusCode.OK, response.StatusCode);
@@ -82,7 +87,7 @@ namespace Microsoft.AspNetCore.StaticFiles
         {
             using (var fileProvider = new PhysicalFileProvider(Path.Combine(AppContext.BaseDirectory, baseDir)))
             {
-                var server = StaticFilesTestServer.Create(
+                using var host = await StaticFilesTestServer.Create(
                     app => app.UseDirectoryBrowser(new DirectoryBrowserOptions
                     {
                         RequestPath = new PathString(baseUrl),
@@ -90,6 +95,7 @@ namespace Microsoft.AspNetCore.StaticFiles
                         RedirectToAppendTrailingSlash = appendTrailingSlash
                     }),
                     services => services.AddDirectoryBrowser());
+                using var server = host.GetTestServer();
                 var response = await server.CreateRequest(requestUrl).GetAsync();
                 Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
             }
@@ -100,7 +106,7 @@ namespace Microsoft.AspNetCore.StaticFiles
         {
             using (var fileProvider = new PhysicalFileProvider(Path.Combine(AppContext.BaseDirectory, ".")))
             {
-                var server = StaticFilesTestServer.Create(
+                using var host = await StaticFilesTestServer.Create(
                     app =>
                     {
                         app.UseRouting();
@@ -128,6 +134,7 @@ namespace Microsoft.AspNetCore.StaticFiles
                         app.UseEndpoints(endpoints => { });
                     },
                     services => { services.AddDirectoryBrowser(); services.AddRouting(); });
+                using var server = host.GetTestServer();
 
                 var response = await server.CreateRequest("/").GetAsync();
                 Assert.Equal(HttpStatusCode.NotAcceptable, response.StatusCode);
@@ -174,7 +181,7 @@ namespace Microsoft.AspNetCore.StaticFiles
         {
             using (var fileProvider = new PhysicalFileProvider(Path.Combine(AppContext.BaseDirectory, baseDir)))
             {
-                var server = StaticFilesTestServer.Create(
+                using var host = await StaticFilesTestServer.Create(
                     app => app.UseDirectoryBrowser(new DirectoryBrowserOptions
                     {
                         RequestPath = new PathString(baseUrl),
@@ -182,6 +189,7 @@ namespace Microsoft.AspNetCore.StaticFiles
                         RedirectToAppendTrailingSlash = appendTrailingSlash,
                     }),
                     services => services.AddDirectoryBrowser());
+                using var server = host.GetTestServer();
                 var response = await server.CreateRequest(requestUrl).GetAsync();
 
                 Assert.Equal(HttpStatusCode.OK, response.StatusCode);
@@ -217,13 +225,14 @@ namespace Microsoft.AspNetCore.StaticFiles
         {
             using (var fileProvider = new PhysicalFileProvider(Path.Combine(AppContext.BaseDirectory, baseDir)))
             {
-                var server = StaticFilesTestServer.Create(
+                using var host = await StaticFilesTestServer.Create(
                     app => app.UseDirectoryBrowser(new DirectoryBrowserOptions
                     {
                         RequestPath = new PathString(baseUrl),
                         FileProvider = fileProvider
                     }),
                     services => services.AddDirectoryBrowser());
+                using var server = host.GetTestServer();
 
                 var response = await server.CreateRequest(requestUrl + queryString).GetAsync();
 
@@ -266,7 +275,7 @@ namespace Microsoft.AspNetCore.StaticFiles
         {
             using (var fileProvider = new PhysicalFileProvider(Path.Combine(AppContext.BaseDirectory, baseDir)))
             {
-                var server = StaticFilesTestServer.Create(
+                using var host = await StaticFilesTestServer.Create(
                     app => app.UseDirectoryBrowser(new DirectoryBrowserOptions
                     {
                         RequestPath = new PathString(baseUrl),
@@ -274,6 +283,7 @@ namespace Microsoft.AspNetCore.StaticFiles
                         RedirectToAppendTrailingSlash = appendTrailingSlash
                     }),
                     services => services.AddDirectoryBrowser());
+                using var server = host.GetTestServer();
 
                 var response = await server.CreateRequest(requestUrl).PostAsync();
                 Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
@@ -313,7 +323,7 @@ namespace Microsoft.AspNetCore.StaticFiles
         {
             using (var fileProvider = new PhysicalFileProvider(Path.Combine(AppContext.BaseDirectory, baseDir)))
             {
-                var server = StaticFilesTestServer.Create(
+                using var host = await StaticFilesTestServer.Create(
                     app => app.UseDirectoryBrowser(new DirectoryBrowserOptions
                     {
                         RequestPath = new PathString(baseUrl),
@@ -321,6 +331,7 @@ namespace Microsoft.AspNetCore.StaticFiles
                         RedirectToAppendTrailingSlash = appendTrailingSlash
                     }),
                     services => services.AddDirectoryBrowser());
+                using var server = host.GetTestServer();
 
                 var response = await server.CreateRequest(requestUrl).SendAsync("HEAD");
 

src/Middleware/StaticFiles/test/UnitTests/RangeHeaderTests.cs

@@ -19,7 +19,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [Fact]
         public async Task IfRangeWithCurrentEtagShouldServePartialContent()
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             HttpResponseMessage original = await server.CreateClient().GetAsync("http://localhost/SubFolder/ranges.txt");
 
             var req = new HttpRequestMessage(HttpMethod.Get, "http://localhost/SubFolder/ranges.txt");
@@ -39,7 +40,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [Fact]
         public async Task HEADIfRangeWithCurrentEtagShouldReturn200Ok()
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             HttpResponseMessage original = await server.CreateClient().GetAsync("http://localhost/SubFolder/ranges.txt");
 
             var req = new HttpRequestMessage(HttpMethod.Head, "http://localhost/SubFolder/ranges.txt");
@@ -59,7 +61,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [Fact]
         public async Task IfRangeWithCurrentDateShouldServePartialContent()
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             HttpResponseMessage original = await server.CreateClient().GetAsync("http://localhost/SubFolder/ranges.txt");
 
             var req = new HttpRequestMessage(HttpMethod.Get, "http://localhost/SubFolder/ranges.txt");
@@ -75,7 +78,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [Fact]
         public async Task IfModifiedSinceWithPastDateShouldServePartialContent()
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             HttpResponseMessage original = await server.CreateClient().GetAsync("http://localhost/SubFolder/ranges.txt");
 
             var req = new HttpRequestMessage(HttpMethod.Get, "http://localhost/SubFolder/ranges.txt");
@@ -91,7 +95,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [Fact]
         public async Task IfModifiedSinceWithCurrentDateShouldReturn304()
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             HttpResponseMessage original = await server.CreateClient().GetAsync("http://localhost/SubFolder/ranges.txt");
 
             var req = new HttpRequestMessage(HttpMethod.Get, "http://localhost/SubFolder/ranges.txt");
@@ -107,7 +112,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [Fact]
         public async Task HEADIfRangeWithCurrentDateShouldReturn200Ok()
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             HttpResponseMessage original = await server.CreateClient().GetAsync("http://localhost/SubFolder/ranges.txt");
 
             var req = new HttpRequestMessage(HttpMethod.Head, "http://localhost/SubFolder/ranges.txt");
@@ -127,7 +133,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [Fact]
         public async Task IfRangeWithOldEtagShouldServeFullContent()
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             var req = new HttpRequestMessage(HttpMethod.Get, "http://localhost/SubFolder/ranges.txt");
             req.Headers.Add("If-Range", "\"OldEtag\"");
             req.Headers.Add("Range", "bytes=0-10");
@@ -143,7 +150,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [Fact]
         public async Task HEADIfRangeWithOldEtagShouldServeFullContent()
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             var req = new HttpRequestMessage(HttpMethod.Head, "http://localhost/SubFolder/ranges.txt");
             req.Headers.Add("If-Range", "\"OldEtag\"");
             req.Headers.Add("Range", "bytes=0-10");
@@ -159,7 +167,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [Fact]
         public async Task IfRangeWithOldDateShouldServeFullContent()
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             HttpResponseMessage original = await server.CreateClient().GetAsync("http://localhost/SubFolder/ranges.txt");
 
             var req = new HttpRequestMessage(HttpMethod.Get, "http://localhost/SubFolder/ranges.txt");
@@ -177,7 +186,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [Fact]
         public async Task HEADIfRangeWithOldDateShouldServeFullContent()
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             HttpResponseMessage original = await server.CreateClient().GetAsync("http://localhost/SubFolder/ranges.txt");
 
             var req = new HttpRequestMessage(HttpMethod.Head, "http://localhost/SubFolder/ranges.txt");
@@ -196,7 +206,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [Fact]
         public async Task IfRangeWithoutRangeShouldServeFullContent()
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             HttpResponseMessage original = await server.CreateClient().GetAsync("http://localhost/SubFolder/ranges.txt");
 
             var req = new HttpRequestMessage(HttpMethod.Get, "http://localhost/SubFolder/ranges.txt");
@@ -222,7 +233,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [Fact]
         public async Task HEADIfRangeWithoutRangeShouldServeFullContent()
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             HttpResponseMessage original = await server.CreateClient().GetAsync("http://localhost/SubFolder/ranges.txt");
 
             var req = new HttpRequestMessage(HttpMethod.Head, "http://localhost/SubFolder/ranges.txt");
@@ -256,7 +268,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [InlineData("-1001", "0-61", 62, "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")]
         public async Task SingleValidRangeShouldServePartialContent(string range, string expectedRange, int length, string expectedData)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             var req = new HttpRequestMessage(HttpMethod.Get, "http://localhost/SubFolder/ranges.txt");
             req.Headers.Add("Range", "bytes=" + range);
             HttpResponseMessage resp = await server.CreateClient().SendAsync(req);
@@ -276,7 +289,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [InlineData("0-2", "0-0", 1, "A")]
         public async Task SingleValidRangeShouldServePartialContentSingleByteFile(string range, string expectedRange, int length, string expectedData)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             var req = new HttpRequestMessage(HttpMethod.Get, "http://localhost/SubFolder/SingleByte.txt");
             req.Headers.Add("Range", "bytes=" + range);
             HttpResponseMessage resp = await server.CreateClient().SendAsync(req);
@@ -296,7 +310,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [InlineData("0-2")]
         public async Task SingleValidRangeShouldServeRequestedRangeNotSatisfiableEmptyFile(string range)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             var req = new HttpRequestMessage(HttpMethod.Get, "http://localhost/SubFolder/Empty.txt");
             req.Headers.Add("Range", "bytes=" + range);
             HttpResponseMessage resp = await server.CreateClient().SendAsync(req);
@@ -309,7 +324,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [InlineData("10-35")]
         public async Task HEADSingleValidRangeShouldReturnOk(string range)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             var req = new HttpRequestMessage(HttpMethod.Head, "http://localhost/SubFolder/ranges.txt");
             req.Headers.Add("Range", "bytes=" + range);
             HttpResponseMessage resp = await server.CreateClient().SendAsync(req);
@@ -326,7 +342,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [InlineData("-0")] // Suffix range must be non-zero
         public async Task SingleNotSatisfiableRange(string range)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             var req = new HttpRequestMessage(HttpMethod.Get, "http://localhost/SubFolder/ranges.txt");
             req.Headers.TryAddWithoutValidation("Range", "bytes=" + range);
             HttpResponseMessage resp = await server.CreateClient().SendAsync(req);
@@ -340,7 +357,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [InlineData("1000-1001")] // Out of range
         public async Task HEADSingleNotSatisfiableRangeReturnsOk(string range)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             var req = new HttpRequestMessage(HttpMethod.Head, "http://localhost/SubFolder/ranges.txt");
             req.Headers.TryAddWithoutValidation("Range", "bytes=" + range);
             HttpResponseMessage resp = await server.CreateClient().SendAsync(req);
@@ -359,7 +377,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [InlineData("a-b")]
         public async Task SingleInvalidRangeIgnored(string range)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             var req = new HttpRequestMessage(HttpMethod.Get, "http://localhost/SubFolder/ranges.txt");
             req.Headers.TryAddWithoutValidation("Range", "bytes=" + range);
             HttpResponseMessage resp = await server.CreateClient().SendAsync(req);
@@ -380,7 +399,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [InlineData("a-b")]
         public async Task HEADSingleInvalidRangeIgnored(string range)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             var req = new HttpRequestMessage(HttpMethod.Head, "http://localhost/SubFolder/ranges.txt");
             req.Headers.TryAddWithoutValidation("Range", "bytes=" + range);
             HttpResponseMessage resp = await server.CreateClient().SendAsync(req);
@@ -400,7 +420,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [InlineData("0-0,6-6,8-8,2-2,4-4")]
         public async Task MultipleValidRangesShouldServeFullContent(string ranges)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             var req = new HttpRequestMessage(HttpMethod.Get, "http://localhost/SubFolder/ranges.txt");
             req.Headers.Add("Range", "bytes=" + ranges);
             HttpResponseMessage resp = await server.CreateClient().SendAsync(req);
@@ -419,7 +440,8 @@ namespace Microsoft.AspNetCore.StaticFiles
         [InlineData("2-2,0-0")] // SHOULD send in the requested order.
         public async Task HEADMultipleValidRangesShouldServeFullContent(string range)
         {
-            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var host = await StaticFilesTestServer.Create(app => app.UseFileServer());
+            using var server = host.GetTestServer();
             var req = new HttpRequestMessage(HttpMethod.Head, "http://localhost/SubFolder/ranges.txt");
             req.Headers.Add("Range", "bytes=" + range);
             HttpResponseMessage resp = await server.CreateClient().SendAsync(req);

src/Middleware/StaticFiles/test/UnitTests/StaticFileMiddlewareTests.cs

@@ -16,6 +16,7 @@ using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.AspNetCore.Testing;
 using Microsoft.Extensions.FileProviders;
+using Microsoft.Extensions.Hosting;
 using Moq;
 using Xunit;
 
@@ -26,9 +27,17 @@ namespace Microsoft.AspNetCore.StaticFiles
         [Fact]
         public async Task ReturnsNotFoundWithoutWwwroot()
         {
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app => app.UseStaticFiles());
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync("/ranges.txt");
 
@@ -47,10 +56,18 @@ namespace Microsoft.AspNetCore.StaticFiles
 
             try
             {
-                var builder = new WebHostBuilder()
+                using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app => app.UseStaticFiles(new StaticFileOptions { ServeUnknownFileTypes = true }))
                     .UseWebRoot(AppContext.BaseDirectory);
-                var server = new TestServer(builder);
+                }).Build();
+
+                await host.StartAsync();
+
+                var server = host.GetTestServer();
 
                 var response = await server.CreateClient().GetAsync(Path.GetFileName(badLink));
 
@@ -70,7 +87,11 @@ namespace Microsoft.AspNetCore.StaticFiles
             mockSendFile.Setup(m => m.SendFileAsync(It.IsAny<string>(), It.IsAny<long>(), It.IsAny<long?>(), It.IsAny<CancellationToken>()))
                 .ThrowsAsync(new FileNotFoundException());
             mockSendFile.Setup(m => m.Stream).Returns(Stream.Null);
-            var builder = new WebHostBuilder()
+            using var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .Configure(app =>
                     {
                         app.Use(async (ctx, next) =>
@@ -81,7 +102,11 @@ namespace Microsoft.AspNetCore.StaticFiles
                         app.UseStaticFiles(new StaticFileOptions { ServeUnknownFileTypes = true });
                     })
                     .UseWebRoot(AppContext.BaseDirectory);
-            var server = new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+
+            var server = host.GetTestServer();
 
             var response = await server.CreateClient().GetAsync("TestDocument.txt");
 
@@ -94,10 +119,11 @@ namespace Microsoft.AspNetCore.StaticFiles
         {
             using (var fileProvider = new PhysicalFileProvider(AppContext.BaseDirectory))
             {
-                var server = StaticFilesTestServer.Create(app => app.UseStaticFiles(new StaticFileOptions
+                using var host = await StaticFilesTestServer.Create(app => app.UseStaticFiles(new StaticFileOptions
                 {
                     FileProvider = fileProvider
                 }));
+                using var server = host.GetTestServer();
                 var fileInfo = fileProvider.GetFileInfo("TestDocument.txt");
                 var response = await server.CreateRequest("TestDocument.txt").GetAsync();
 
@@ -112,13 +138,16 @@ namespace Microsoft.AspNetCore.StaticFiles
         public async Task NullArguments()
         {
             // No exception, default provided
-            StaticFilesTestServer.Create(app => app.UseStaticFiles(new StaticFileOptions { ContentTypeProvider = null }));
+            using (await StaticFilesTestServer.Create(app => app.UseStaticFiles(new StaticFileOptions { ContentTypeProvider = null })))
+            { }
 
             // No exception, default provided
-            StaticFilesTestServer.Create(app => app.UseStaticFiles(new StaticFileOptions { FileProvider = null }));
+            using (await StaticFilesTestServer.Create(app => app.UseStaticFiles(new StaticFileOptions { FileProvider = null })))
+            { }
 
             // PathString(null) is OK.
-            var server = StaticFilesTestServer.Create(app => app.UseStaticFiles((string)null));
+            using var host = await StaticFilesTestServer.Create(app => app.UseStaticFiles((string)null));
+            using var server = host.GetTestServer();
             var response = await server.CreateClient().GetAsync("/");
             Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
         }
@@ -146,11 +175,12 @@ namespace Microsoft.AspNetCore.StaticFiles
         {
             using (var fileProvider = new PhysicalFileProvider(Path.Combine(AppContext.BaseDirectory, baseDir)))
             {
-                var server = StaticFilesTestServer.Create(app => app.UseStaticFiles(new StaticFileOptions
+                using var host = await StaticFilesTestServer.Create(app => app.UseStaticFiles(new StaticFileOptions
                 {
                     RequestPath = new PathString(baseUrl),
                     FileProvider = fileProvider
                 }));
+                using var server = host.GetTestServer();
                 var fileInfo = fileProvider.GetFileInfo(Path.GetFileName(requestUrl));
                 var response = await server.CreateRequest(requestUrl).GetAsync();
                 var responseContent = await response.Content.ReadAsByteArrayAsync();
@@ -176,11 +206,12 @@ namespace Microsoft.AspNetCore.StaticFiles
         {
             using (var fileProvider = new PhysicalFileProvider(Path.Combine(AppContext.BaseDirectory, baseDir)))
             {
-                var server = StaticFilesTestServer.Create(app => app.UseStaticFiles(new StaticFileOptions
+                using var host = await StaticFilesTestServer.Create(app => app.UseStaticFiles(new StaticFileOptions
                 {
                     RequestPath = new PathString(baseUrl),
                     FileProvider = fileProvider
                 }));
+                using var server = host.GetTestServer();
                 var fileInfo = fileProvider.GetFileInfo(Path.GetFileName(requestUrl));
                 var response = await server.CreateRequest(requestUrl).SendAsync("HEAD");
 
@@ -235,11 +266,12 @@ namespace Microsoft.AspNetCore.StaticFiles
         {
             using (var fileProvider = new PhysicalFileProvider(Path.Combine(AppContext.BaseDirectory, baseDir)))
             {
-                var server = StaticFilesTestServer.Create(app => app.UseStaticFiles(new StaticFileOptions
+                using var host = await StaticFilesTestServer.Create(app => app.UseStaticFiles(new StaticFileOptions
                 {
                     RequestPath = new PathString(baseUrl),
                     FileProvider = fileProvider
                 }));
+                using var server = host.GetTestServer();
                 var response = await server.CreateRequest(requestUrl).SendAsync(method);
                 Assert.Null(response.Content.Headers.LastModified);
                 Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);

src/Middleware/StaticFiles/test/UnitTests/StaticFilesTestServer.cs

@@ -4,17 +4,19 @@
 using System;
 using System.Collections.Generic;
 using System.Runtime.InteropServices;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 
 namespace Microsoft.AspNetCore.StaticFiles
 {
     public static class StaticFilesTestServer
     {
-        public static TestServer Create(Action<IApplicationBuilder> configureApp, Action<IServiceCollection> configureServices = null)
+        public static async Task<IHost> Create(Action<IApplicationBuilder> configureApp, Action<IServiceCollection> configureServices = null)
         {
             Action<IServiceCollection> defaultConfigureServices = services => { };
             var configuration = new ConfigurationBuilder()
@@ -23,11 +25,18 @@ namespace Microsoft.AspNetCore.StaticFiles
                     new KeyValuePair<string, string>("webroot", ".")
                 })
                 .Build();
-            var builder = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                    .UseTestServer()
                     .UseConfiguration(configuration)
                     .Configure(configureApp)
                     .ConfigureServices(configureServices ?? defaultConfigureServices);
-            return new TestServer(builder);
+                }).Build();
+
+            await host.StartAsync();
+            return host;
         }
     }
 }

src/Middleware/WebSockets/samples/EchoApp/Program.cs

@@ -1,24 +1,26 @@
-using System;
-using System.Collections.Generic;
 using System.IO;
-using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Hosting;
+using Microsoft.Extensions.Hosting;
 
 namespace EchoApp
 {
     public class Program
     {
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .UseKestrel()
                     .UseContentRoot(Directory.GetCurrentDirectory())
                     .UseIISIntegration()
-                .UseStartup<Startup>()
+                    .UseStartup<Startup>();
+                })
                 .Build();
 
-            host.Run();
+            return host.RunAsync();
         }
     }
 }

src/Middleware/WebSockets/test/ConformanceTests/AutobahnTestApp/Program.cs

@@ -1,34 +1,38 @@
 using System;
 using System.IO;
 using System.Net;
-using System.Runtime.Loader;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 
 namespace AutobahnTestApp
 {
     public class Program
     {
-        public static void Main(string[] args)
+        public static Task Main(string[] args)
         {
             var scenarioName = "Unknown";
             var config = new ConfigurationBuilder()
                 .AddCommandLine(args)
                 .Build();
 
-            var builder = new WebHostBuilder()
+            var builder = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .ConfigureLogging(loggingBuilder => loggingBuilder.AddConsole())
                     .UseConfiguration(config)
                     .UseContentRoot(Directory.GetCurrentDirectory())
                     .UseIISIntegration()
                     .UseStartup<Startup>();
 
-            if (string.Equals(builder.GetSetting("server"), "Microsoft.AspNetCore.Server.HttpSys", System.StringComparison.Ordinal))
+                    if (string.Equals(webHostBuilder.GetSetting("server"), "Microsoft.AspNetCore.Server.HttpSys", System.StringComparison.Ordinal))
                     {
                         scenarioName = "HttpSysServer";
                         Console.WriteLine("Using HttpSys server");
-                builder.UseHttpSys();
+                        webHostBuilder.UseHttpSys();
                     }
                     else if (!string.IsNullOrEmpty(Environment.GetEnvironmentVariable("ASPNETCORE_PORT")))
                     {
@@ -36,13 +40,13 @@ namespace AutobahnTestApp
                         // The port will not yet be configured at this point, but will also not require HTTPS.
                         scenarioName = "AspNetCoreModule";
                         Console.WriteLine("Detected ANCM, using Kestrel");
-                builder.UseKestrel();
+                        webHostBuilder.UseKestrel();
                     }
                     else
                     {
                         // Also check "server.urls" for back-compat.
-                var urls = builder.GetSetting(WebHostDefaults.ServerUrlsKey) ?? builder.GetSetting("server.urls");
-                builder.UseSetting(WebHostDefaults.ServerUrlsKey, string.Empty);
+                        var urls = webHostBuilder.GetSetting(WebHostDefaults.ServerUrlsKey) ?? webHostBuilder.GetSetting("server.urls");
+                        webHostBuilder.UseSetting(WebHostDefaults.ServerUrlsKey, string.Empty);
 
                         Console.WriteLine($"Using Kestrel, URL: {urls}");
 
@@ -53,7 +57,7 @@ namespace AutobahnTestApp
 
                         var uri = new Uri(urls);
 
-                builder.UseKestrel(options =>
+                        webHostBuilder.UseKestrel(options =>
                         {
                             options.Listen(IPAddress.Loopback, uri.Port, listenOptions =>
                             {
@@ -71,6 +75,7 @@ namespace AutobahnTestApp
                             });
                         });
                     }
+                });
 
             var host = builder.Build();
 
@@ -80,7 +85,7 @@ namespace AutobahnTestApp
             };
 
             Console.WriteLine($"Starting Server for Scenario: {scenarioName}");
-            host.Run();
+            return host.RunAsync();
         }
     }
 }

src/Middleware/WebSockets/test/UnitTests/IHostPortExtensions.cs

@@ -0,0 +1,33 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.AspNetCore.Hosting.Server;
+using Microsoft.AspNetCore.Hosting.Server.Features;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+
+namespace Microsoft.AspNetCore.Hosting
+{
+    public static class IHostPortExtensions
+    {
+        public static int GetPort(this IHost host)
+        {
+            return host.GetPorts().First();
+        }
+
+        public static IEnumerable<int> GetPorts(this IHost host)
+        {
+            return host.GetUris()
+                .Select(u => u.Port);
+        }
+
+        public static IEnumerable<Uri> GetUris(this IHost host)
+        {
+            return host.Services.GetService<IServer>().Features.Get<IServerAddressesFeature>().Addresses
+                .Select(a => new Uri(a));
+        }
+    }
+}

src/Middleware/WebSockets/test/UnitTests/IWebHostPortExtensions.cs

@@ -1,30 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using Microsoft.AspNetCore.Hosting.Server.Features;
-
-namespace Microsoft.AspNetCore.Hosting
-{
-    public static class IWebHostPortExtensions
-    {
-        public static int GetPort(this IWebHost host)
-        {
-            return host.GetPorts().First();
-        }
-
-        public static IEnumerable<int> GetPorts(this IWebHost host)
-        {
-            return host.GetUris()
-                .Select(u => u.Port);
-        }
-
-        public static IEnumerable<Uri> GetUris(this IWebHost host)
-        {
-            return host.ServerFeatures.Get<IServerAddressesFeature>().Addresses
-                .Select(a => new Uri(a));
-        }
-    }
-}

src/Middleware/WebSockets/test/UnitTests/KestrelWebSocketHelpers.cs

@@ -9,6 +9,7 @@ using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 
 namespace Microsoft.AspNetCore.WebSockets.Test
 {
@@ -48,7 +49,10 @@ namespace Microsoft.AspNetCore.WebSockets.Test
             var config = configBuilder.Build();
             config["server.urls"] = $"http://127.0.0.1:0";
 
-            var host = new WebHostBuilder()
+            var host = new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
                     .ConfigureServices(s =>
                     {
                         s.AddWebSockets(configure);
@@ -56,8 +60,8 @@ namespace Microsoft.AspNetCore.WebSockets.Test
                     })
                     .UseConfiguration(config)
                     .UseKestrel()
-                .Configure(startup)
-                .Build();
+                    .Configure(startup);
+                }).Build();
 
             host.Start();
             port = host.GetPort();