Test code nitpicks.

test/Microsoft.AspNetCore.Server.KestrelTests/BadHttpRequestTests.cs

@@ -2,6 +2,7 @@
 // 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.Server.Kestrel.Infrastructure;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Server.KestrelTests
@@ -68,7 +69,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
         [InlineData("GET / HTTP/1.0\rA")]
         public async Task TestBadRequestLines(string request)
         {
-            using (var server = new TestServer(context => { return Task.FromResult(0); }))
+            using (var server = new TestServer(context => TaskUtilities.CompletedTask))
             {
                 using (var connection = server.CreateConnection())
                 {
@@ -85,7 +86,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
         [InlineData("GET / HTTP/1.0\rA")]
         public async Task ServerClosesConnectionAsSoonAsBadRequestLineIsDetected(string request)
         {
-            using (var server = new TestServer(context => { return Task.FromResult(0); }))
+            using (var server = new TestServer(context => TaskUtilities.CompletedTask))
             {
                 using (var connection = server.CreateConnection())
                 {

test/Microsoft.AspNetCore.Server.KestrelTests/EngineTests.cs

@@ -11,6 +11,7 @@ using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.Server.Kestrel;
+using Microsoft.AspNetCore.Server.Kestrel.Infrastructure;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Server.KestrelTests
@@ -1062,7 +1063,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
             using (var server = new TestServer(httpContext =>
             {
                 httpContext.Abort();
-                return Task.FromResult(0);
+                return TaskUtilities.CompletedTask;
             }, testContext))
             {
                 using (var connection = server.CreateConnection())

test/Microsoft.AspNetCore.Server.KestrelTests/HttpsConnectionFilterTests.cs

@@ -16,6 +16,7 @@ using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.Server.Kestrel.Filter;
 using Microsoft.AspNetCore.Server.Kestrel.Https;
+using Microsoft.AspNetCore.Server.Kestrel.Infrastructure;
 using Microsoft.AspNetCore.Testing.xunit;
 using Xunit;
 
@@ -116,13 +117,12 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 new NoOpConnectionFilter())
             );
 
-            RequestDelegate app = context =>
+            using (var server = new TestServer(context =>
-            {
+                {
-                Assert.Equal(context.Features.Get<ITlsConnectionFeature>(), null);
+                    Assert.Equal(context.Features.Get<ITlsConnectionFeature>(), null);
-                return context.Response.WriteAsync("hello world");
+                    return context.Response.WriteAsync("hello world");
-            };
+                },
-
+                serviceContext, _serverAddress))
-            using (var server = new TestServer(app, serviceContext, _serverAddress))
             {
                 using (var client = new HttpClient(GetHandler()))
                 {
@@ -153,8 +153,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 new NoOpConnectionFilter())
             );
 
-            RequestDelegate app = context => Task.FromResult(0);
+            using (var server = new TestServer(context => TaskUtilities.CompletedTask, serviceContext, _serverAddress))
-            using (var server = new TestServer(app, serviceContext, _serverAddress))
             {
                 using (var client = new TcpClient())
                 {
@@ -182,16 +181,15 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 new NoOpConnectionFilter())
             );
 
-            RequestDelegate app = context =>
+            using (var server = new TestServer(context =>
-            {
+                {
-                var tlsFeature = context.Features.Get<ITlsConnectionFeature>();
+                    var tlsFeature = context.Features.Get<ITlsConnectionFeature>();
-                Assert.NotNull(tlsFeature);
+                    Assert.NotNull(tlsFeature);
-                Assert.NotNull(tlsFeature.ClientCertificate);
+                    Assert.NotNull(tlsFeature.ClientCertificate);
-                Assert.NotNull(context.Connection.ClientCertificate);
+                    Assert.NotNull(context.Connection.ClientCertificate);
-                return context.Response.WriteAsync("hello world");
+                    return context.Response.WriteAsync("hello world");
-            };
+                },
-
+                serviceContext, _serverAddress))
-            using (var server = new TestServer(app, serviceContext, _serverAddress))
             {
                 using (var client = new TcpClient())
                 {
@@ -219,9 +217,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                     new NoOpConnectionFilter())
             );
 
-            RequestDelegate app = context => context.Response.WriteAsync(context.Request.Scheme);
+            using (var server = new TestServer(context => context.Response.WriteAsync(context.Request.Scheme), serviceContext, _serverAddress))
-
-            using (var server = new TestServer(app, serviceContext, _serverAddress))
             {
                 using (var client = new HttpClient(GetHandler()))
                 {
@@ -245,12 +241,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 new NoOpConnectionFilter())
             );
 
-            RequestDelegate app = context =>
+            using (var server = new TestServer(context => context.Response.WriteAsync("hello world"), serviceContext, _serverAddress))
-            {
-                return context.Response.WriteAsync("hello world");
-            };
-
-            using (var server = new TestServer(app, serviceContext, _serverAddress))
             {
                 // SslStream is used to ensure the certificate is actually passed to the server
                 // HttpClient might not send the certificate because it is invalid or it doesn't match any
@@ -286,9 +277,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 new NoOpConnectionFilter())
             );
 
-            RequestDelegate app = context => Task.FromResult(0);
+            using (var server = new TestServer(context => TaskUtilities.CompletedTask, serviceContext, _serverAddress))
-
-            using (var server = new TestServer(app, serviceContext, _serverAddress))
             {
                 using (var client = new TcpClient())
                 {
@@ -315,9 +304,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 new NoOpConnectionFilter())
             );
 
-            RequestDelegate app = context => Task.FromResult(0);
+            using (var server = new TestServer(context => TaskUtilities.CompletedTask, serviceContext, _serverAddress))
-
-            using (var server = new TestServer(app, serviceContext, _serverAddress))
             {
                 using (var client = new TcpClient())
                 {
@@ -342,9 +329,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 new NoOpConnectionFilter())
             );
 
-            RequestDelegate app = context => Task.FromResult(0);
+            using (var server = new TestServer(context => TaskUtilities.CompletedTask, serviceContext, _serverAddress))
-
-            using (var server = new TestServer(app, serviceContext, _serverAddress))
             {
                 using (var client = new TcpClient())
                 {

test/Microsoft.AspNetCore.Server.KestrelTests/TestHelpers/MockFrameControl.cs

@@ -5,6 +5,7 @@ using System;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Server.Kestrel.Http;
+using Microsoft.AspNetCore.Server.Kestrel.Infrastructure;
 
 namespace Microsoft.AspNetCore.Server.KestrelTests.TestHelpers
 {
@@ -16,7 +17,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests.TestHelpers
 
         public Task FlushAsync(CancellationToken cancellationToken)
         {
-            return Task.FromResult(0);
+            return TaskUtilities.CompletedTask;
         }
 
         public void ProduceContinue()
@@ -29,7 +30,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests.TestHelpers
 
         public Task WriteAsync(ArraySegment<byte> data, CancellationToken cancellationToken)
         {
-            return Task.FromResult(0);
+            return TaskUtilities.CompletedTask;
         }
     }
 }

test/Microsoft.AspNetCore.Server.KestrelTests/TestHelpers/MockSocketOuptut.cs

@@ -26,7 +26,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests.TestHelpers
 
         public Task WriteAsync(ArraySegment<byte> buffer, bool chunk = false, CancellationToken cancellationToken = default(CancellationToken))
         {
-            return Task.FromResult(0);
+            return TaskUtilities.CompletedTask;
         }
     }
 }

test/Microsoft.AspNetCore.Server.KestrelTests/TestInput.cs

@@ -76,7 +76,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
 
         Task IFrameControl.WriteAsync(ArraySegment<byte> data, CancellationToken cancellationToken)
         {
-            return Task.FromResult(0);
+            return TaskUtilities.CompletedTask;
         }
 
         void IFrameControl.Flush()
@@ -85,7 +85,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
 
         Task IFrameControl.FlushAsync(CancellationToken cancellationToken)
         {
-            return Task.FromResult(0);
+            return TaskUtilities.CompletedTask;
         }
 
         public void Dispose()