Fix flaky dispatcher test

src/Microsoft.AspNetCore.Razor.Tools/DefaultRequestDispatcher.cs

@@ -383,6 +383,8 @@ namespace Microsoft.AspNetCore.Razor.Tools
                                 ServerLogger.Log("End writing response.");
 
                                 reason = ConnectionResult.Reason.CompilationCompleted;
+
+                                _eventBus.CompilationCompleted();
                             }
                             catch
                             {

src/Microsoft.AspNetCore.Razor.Tools/EventBus.cs

@@ -37,6 +37,13 @@ namespace Microsoft.AspNetCore.Razor.Tools
         public virtual void ConnectionCompleted(int count)
         {
         }
+        
+        /// <summary>
+        /// Called when a compilation is completed successfully and the response is written to the stream.
+        /// </summary>
+        public virtual void CompilationCompleted()
+        {
+        }
 
         /// <summary>
         /// Called when a bad client connection was detected and the server will be shutting down as a 

test/Microsoft.AspNetCore.Razor.Tools.Test/DefaultRequestDispatcherTest.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Moq;
@@ -335,7 +336,7 @@ namespace Microsoft.AspNetCore.Razor.Tools
         /// <summary>
         /// Ensure server respects keep alive and shuts down after processing simultaneous connections.
         /// </summary>
-        [Fact(Skip = "https://github.com/aspnet/Razor/issues/2018")]
+        [Fact]
         public async Task Dispatcher_ProcessSimultaneousConnections_HitsKeepAliveTimeout()
         {
             // Arrange
@@ -352,6 +353,7 @@ namespace Microsoft.AspNetCore.Razor.Tools
                         var source = new TaskCompletionSource<bool>();
                         var connectionTask = CreateConnectionWithEmptyServerRequest(c =>
                         {
+                            // Keep the connection active until we decide to end it.
                             c.WaitForDisconnectAsyncFunc = _ => source.Task;
                         });
                         list.Add(source);
@@ -370,24 +372,42 @@ namespace Microsoft.AspNetCore.Razor.Tools
                 };
             });
 
-            var keepAlive = TimeSpan.FromSeconds(1);
             var eventBus = new TestableEventBus();
+            var completedCompilations = 0;
+            var allCompilationsComplete = new TaskCompletionSource<bool>();
+            eventBus.CompilationComplete += (obj, args) =>
+            {
+                if (++completedCompilations == totalCount)
+                {
+                    // All compilations have completed.
+                    allCompilationsComplete.SetResult(true);
+                }
+            };
+            var keepAlive = TimeSpan.FromSeconds(1);
             var dispatcherTask = Task.Run(() =>
             {
                 var dispatcher = new DefaultRequestDispatcher(connectionHost.Object, compilerHost, CancellationToken.None, eventBus, keepAlive);
                 dispatcher.Run();
             });
 
+            // Wait for all connections to be created.
             await readySource.Task;
+
+            // Wait for all compilations to complete.
+            await allCompilationsComplete.Task;
+
+            // Now allow all the connections to be disconnected.
             foreach (var source in list)
             {
                 source.SetResult(true);
             }
 
             // Act
+            // Now dispatcher should be in an idle state with no active connections.
             await dispatcherTask;
 
             // Assert
+            Assert.False(eventBus.HasDetectedBadConnection);
             Assert.Equal(totalCount, eventBus.CompletedCount);
             Assert.True(eventBus.LastProcessedTime.HasValue, "LastProcessedTime should have had a value.");
             Assert.True(eventBus.HitKeepAliveTimeout, "HitKeepAliveTimeout should have been hit.");

test/Microsoft.AspNetCore.Razor.Tools.Test/Infrastructure/TestableEventBus.cs

@@ -2,21 +2,27 @@
 // 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.Text;
 
 namespace Microsoft.AspNetCore.Razor.Tools
 {
     internal class TestableEventBus : EventBus
     {
-        public int ListeningCount;
-        public int ConnectionCount;
-        public int CompletedCount;
-        public DateTime? LastProcessedTime;
-        public TimeSpan? KeepAlive;
-        public bool HasDetectedBadConnection;
-        public bool HitKeepAliveTimeout;
         public event EventHandler Listening;
+        public event EventHandler CompilationComplete;
+
+        public int ListeningCount { get; private set; }
+
+        public int ConnectionCount { get; private set; }
+
+        public int CompletedCount { get; private set; }
+
+        public DateTime? LastProcessedTime { get; private set; }
+
+        public TimeSpan? KeepAlive { get; private set; }
+
+        public bool HasDetectedBadConnection { get; private set; }
+
+        public bool HitKeepAliveTimeout { get; private set; }
 
         public override void ConnectionListening()
         {
@@ -35,6 +41,11 @@ namespace Microsoft.AspNetCore.Razor.Tools
             LastProcessedTime = DateTime.Now;
         }
 
+        public override void CompilationCompleted()
+        {
+            CompilationComplete?.Invoke(this, EventArgs.Empty);
+        }
+
         public override void UpdateKeepAlive(TimeSpan timeSpan)
         {
             KeepAlive = timeSpan;

test/Microsoft.AspNetCore.Razor.Tools.Test/ServerLifecycleTest.cs

@@ -116,7 +116,8 @@ namespace Microsoft.AspNetCore.Razor.Tools
         /// A shutdown request should not abort an existing compilation.  It should be allowed to run to 
         /// completion.
         /// </summary>
-        [ConditionalFact(Skip = "Skipping temporarily on non-windows. https://github.com/aspnet/Razor/issues/1991")]
+        // Skipping temporarily on non-windows. https://github.com/aspnet/Razor/issues/1991
+        [ConditionalFact]
         [OSSkipCondition(OperatingSystems.Linux | OperatingSystems.MacOSX)]
         public async Task ServerRunning_ShutdownRequest_DoesNotAbortCompilation()
         {
@@ -153,7 +154,8 @@ namespace Microsoft.AspNetCore.Razor.Tools
         /// <summary>
         /// Multiple clients should be able to send shutdown requests to the server.
         /// </summary>
-        [ConditionalFact(Skip = "Skipping temporarily on non-windows. https://github.com/aspnet/Razor/issues/1991")]
+        // Skipping temporarily on non-windows. https://github.com/aspnet/Razor/issues/1991
+        [ConditionalFact]
         [OSSkipCondition(OperatingSystems.Linux | OperatingSystems.MacOSX)]
         public async Task ServerRunning_MultipleShutdownRequests_HandlesSuccessfully()
         {
@@ -191,7 +193,8 @@ namespace Microsoft.AspNetCore.Razor.Tools
             }
         }
 
-        [ConditionalFact(Skip = "Skipping temporarily on non-windows. https://github.com/aspnet/Razor/issues/1991")]
+        // Skipping temporarily on non-windows. https://github.com/aspnet/Razor/issues/1991
+        [ConditionalFact]
         [OSSkipCondition(OperatingSystems.Linux | OperatingSystems.MacOSX)]
         public async Task ServerRunning_CancelCompilation_CancelsSuccessfully()
         {