diff --git a/test/Microsoft.AspNetCore.Server.KestrelTests/SocketOutputTests.cs b/test/Microsoft.AspNetCore.Server.KestrelTests/SocketOutputTests.cs
index 639d52741f..ff26864bc5 100644
--- a/test/Microsoft.AspNetCore.Server.KestrelTests/SocketOutputTests.cs
+++ b/test/Microsoft.AspNetCore.Server.KestrelTests/SocketOutputTests.cs
@@ -2,10 +2,10 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Threading;
 using System.Threading.Tasks;
-using Microsoft.AspNetCore.Server.Kestrel;
 using Microsoft.AspNetCore.Server.Kestrel.Internal;
 using Microsoft.AspNetCore.Server.Kestrel.Internal.Http;
 using Microsoft.AspNetCore.Server.Kestrel.Internal.Infrastructure;
@@ -66,7 +66,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
         {
             // This should match _maxBytesPreCompleted in SocketOutput
             var maxBytesPreCompleted = 65536;
-            var completeQueue = new Queue<Action<int>>();
+            var completeQueue = new ConcurrentQueue<Action<int>>();
 
             // Arrange
             var mockLibuv = new MockLibuv
@@ -87,7 +87,8 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 var socket = new MockSocket(mockLibuv, kestrelThread.Loop.ThreadId, new TestKestrelTrace());
                 var trace = new KestrelTrace(new TestKestrelTrace());
                 var ltp = new LoggingThreadPool(trace);
-                var socketOutput = new SocketOutput(kestrelThread, socket, memory, new MockConnection(), "0", trace, ltp, new Queue<UvWriteReq>());
+                var mockConnection = new MockConnection();
+                var socketOutput = new SocketOutput(kestrelThread, socket, memory, mockConnection, "0", trace, ltp, new Queue<UvWriteReq>());
 
                 var bufferSize = maxBytesPreCompleted;
                 var buffer = new ArraySegment<byte>(new byte[bufferSize], 0, bufferSize);
@@ -111,7 +112,9 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 // Too many bytes are already pre-completed for the second write to pre-complete.
                 Assert.False(completedWh.Wait(1000));
                 // Act
-                completeQueue.Dequeue()(0);
+                Action<int> triggerNextCompleted;
+                Assert.True(completeQueue.TryDequeue(out triggerNextCompleted));
+                triggerNextCompleted(0);
                 // Assert
                 // Finishing the first write should allow the second write to pre-complete.
                 Assert.True(completedWh.Wait(1000));
@@ -120,6 +123,9 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 var cleanupTask = socketOutput.WriteAsync(
                     default(ArraySegment<byte>), default(CancellationToken), socketDisconnect: true);
 
+                // Wait for all writes to complete so the completeQueue isn't modified during enumeration.
+                Assert.True(mockConnection.SocketClosed.Wait(1000));
+
                 foreach (var triggerCompleted in completeQueue)
                 {
                     triggerCompleted(0);
@@ -132,7 +138,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
         {
             // This should match _maxBytesPreCompleted in SocketOutput
             var maxBytesPreCompleted = 65536;
-            var completeQueue = new Queue<Action<int>>();
+            var completeQueue = new ConcurrentQueue<Action<int>>();
             var writeRequestedWh = new ManualResetEventSlim();
 
             // Arrange
@@ -155,7 +161,8 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 var socket = new MockSocket(mockLibuv, kestrelThread.Loop.ThreadId, new TestKestrelTrace());
                 var trace = new KestrelTrace(new TestKestrelTrace());
                 var ltp = new LoggingThreadPool(trace);
-                var socketOutput = new SocketOutput(kestrelThread, socket, memory, new MockConnection(), "0", trace, ltp, new Queue<UvWriteReq>());
+                var mockConnection = new MockConnection();
+                var socketOutput = new SocketOutput(kestrelThread, socket, memory, mockConnection, "0", trace, ltp, new Queue<UvWriteReq>());
 
                 var bufferSize = maxBytesPreCompleted / 2;
                 var data = new byte[bufferSize];
@@ -185,7 +192,9 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 Assert.Equal(2, completeQueue.Count);
 
                 // Act
-                completeQueue.Dequeue()(0);
+                Action<int> triggerNextCompleted;
+                Assert.True(completeQueue.TryDequeue(out triggerNextCompleted));
+                triggerNextCompleted(0);
 
                 // Assert
                 // Finishing the first write should allow the second write to pre-complete.
@@ -195,6 +204,9 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 var cleanupTask = socketOutput.WriteAsync(
                     default(ArraySegment<byte>), default(CancellationToken), socketDisconnect: true);
 
+                // Wait for all writes to complete so the completeQueue isn't modified during enumeration.
+                Assert.True(mockConnection.SocketClosed.Wait(1000));
+
                 foreach (var triggerCompleted in completeQueue)
                 {
                     triggerCompleted(0);
@@ -207,7 +219,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
         {
             // This should match _maxBytesPreCompleted in SocketOutput
             var maxBytesPreCompleted = 65536;
-            var completeQueue = new Queue<Action<int>>();
+            var completeQueue = new ConcurrentQueue<Action<int>>();
 
             // Arrange
             var mockLibuv = new MockLibuv
@@ -298,12 +310,19 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                     Assert.False(task6Success.IsCanceled);
                     Assert.False(task6Success.IsFaulted);
 
-                    Assert.True(true);
-
                     // Cleanup
                     var cleanupTask = ((SocketOutput)socketOutput).WriteAsync(
                         default(ArraySegment<byte>), default(CancellationToken), socketDisconnect: true);
 
+                    // Allow for the socketDisconnect command to get posted to the libuv thread.
+                    // Right now, the up to three pending writes are holding it up.
+                    Action<int> triggerNextCompleted;
+                    Assert.True(completeQueue.TryDequeue(out triggerNextCompleted));
+                    triggerNextCompleted(0);
+
+                    // Wait for all writes to complete so the completeQueue isn't modified during enumeration.
+                    Assert.True(mockConnection.SocketClosed.Wait(1000));
+
                     foreach (var triggerCompleted in completeQueue)
                     {
                         triggerCompleted(0);
@@ -317,7 +336,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
         {
             // This should match _maxBytesPreCompleted in SocketOutput
             var maxBytesPreCompleted = 65536;
-            var completeQueue = new Queue<Action<int>>();
+            var completeQueue = new ConcurrentQueue<Action<int>>();
 
             // Arrange
             var mockLibuv = new MockLibuv
@@ -376,7 +395,9 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                     Assert.False(task3Canceled.IsFaulted);
 
                     // Cause the first write to fail.
-                    completeQueue.Dequeue()(-1);
+                    Action<int> triggerNextCompleted;
+                    Assert.True(completeQueue.TryDequeue(out triggerNextCompleted));
+                    triggerNextCompleted(-1);
 
                     // Second task is now completed
                     await task2Success;
@@ -389,6 +410,9 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                     var cleanupTask = ((SocketOutput)socketOutput).WriteAsync(
                         default(ArraySegment<byte>), default(CancellationToken), socketDisconnect: true);
 
+                    // Wait for all writes to complete so the completeQueue isn't modified during enumeration.
+                    Assert.True(mockConnection.SocketClosed.Wait(1000));
+
                     foreach (var triggerCompleted in completeQueue)
                     {
                         triggerCompleted(0);
@@ -402,7 +426,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
         {
             // This should match _maxBytesPreCompleted in SocketOutput
             var maxBytesPreCompleted = 65536;
-            var completeQueue = new Queue<Action<int>>();
+            var completeQueue = new ConcurrentQueue<Action<int>>();
             var onWriteWh = new ManualResetEventSlim();
 
             // Arrange
@@ -426,7 +450,8 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 var socket = new MockSocket(mockLibuv, kestrelThread.Loop.ThreadId, new TestKestrelTrace());
                 var trace = new KestrelTrace(new TestKestrelTrace());
                 var ltp = new LoggingThreadPool(trace);
-                var socketOutput = new SocketOutput(kestrelThread, socket, memory, new MockConnection(), "0", trace, ltp, new Queue<UvWriteReq>());
+                var mockConnection = new MockConnection();
+                var socketOutput = new SocketOutput(kestrelThread, socket, memory, mockConnection, "0", trace, ltp, new Queue<UvWriteReq>());
 
                 var bufferSize = maxBytesPreCompleted;
                 var buffer = new ArraySegment<byte>(new byte[bufferSize], 0, bufferSize);
@@ -460,7 +485,9 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 socketOutput.WriteAsync(buffer, default(CancellationToken)).ContinueWith(onCompleted2);
 
                 Assert.True(onWriteWh.Wait(1000));
-                completeQueue.Dequeue()(0);
+                Action<int> triggerNextCompleted;
+                Assert.True(completeQueue.TryDequeue(out triggerNextCompleted));
+                triggerNextCompleted(0);
 
                 // Assert 
                 // Too many bytes are already pre-completed for the third but not the second write to pre-complete.
@@ -469,7 +496,8 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 Assert.False(completedWh2.Wait(1000));
 
                 // Act
-                completeQueue.Dequeue()(0);
+                Assert.True(completeQueue.TryDequeue(out triggerNextCompleted));
+                triggerNextCompleted(0);
 
                 // Assert
                 // Finishing the first write should allow the second write to pre-complete.
@@ -479,6 +507,9 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 var cleanupTask = ((SocketOutput)socketOutput).WriteAsync(
                     default(ArraySegment<byte>), default(CancellationToken), socketDisconnect: true);
 
+                // Wait for all writes to complete so the completeQueue isn't modified during enumeration.
+                Assert.True(mockConnection.SocketClosed.Wait(1000));
+
                 foreach (var triggerCompleted in completeQueue)
                 {
                     triggerCompleted(0);
@@ -543,7 +574,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
         public void OnlyAllowsUpToThreeConcurrentWrites()
         {
             var writeWh = new ManualResetEventSlim();
-            var completeQueue = new Queue<Action<int>>();
+            var completeQueue = new ConcurrentQueue<Action<int>>();
 
             var mockLibuv = new MockLibuv
             {
@@ -564,7 +595,8 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 var socket = new MockSocket(mockLibuv, kestrelThread.Loop.ThreadId, new TestKestrelTrace());
                 var trace = new KestrelTrace(new TestKestrelTrace());
                 var ltp = new LoggingThreadPool(trace);
-                var socketOutput = new SocketOutput(kestrelThread, socket, memory, new MockConnection(), "0", trace, ltp, new Queue<UvWriteReq>());
+                var mockConnection = new MockConnection();
+                var socketOutput = new SocketOutput(kestrelThread, socket, memory, mockConnection, "0", trace, ltp, new Queue<UvWriteReq>());
 
                 var buffer = new ArraySegment<byte>(new byte[1]);
 
@@ -584,13 +616,22 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                 Assert.False(writeWh.Wait(1000));
 
                 // Complete 1st write allowing uv_write to be triggered again
-                completeQueue.Dequeue()(0);
+                Action<int> triggerNextCompleted;
+                Assert.True(completeQueue.TryDequeue(out triggerNextCompleted));
+                triggerNextCompleted(0);
                 Assert.True(writeWh.Wait(1000));
 
                 // Cleanup
                 var cleanupTask = socketOutput.WriteAsync(
                     default(ArraySegment<byte>), default(CancellationToken), socketDisconnect: true);
 
+                // Allow for the socketDisconnect command to get posted to the libuv thread.
+                // Right now, the three pending writes are holding it up.
+                Assert.True(completeQueue.TryDequeue(out triggerNextCompleted));
+                triggerNextCompleted(0);
+                // Wait for all writes to complete so the completeQueue isn't modified during enumeration.
+                Assert.True(mockConnection.SocketClosed.Wait(1000));
+
                 foreach (var triggerCompleted in completeQueue)
                 {
                     triggerCompleted(0);