Fixed deadlock issues with TaskCompletionSource, Test passes locally now!

Author: michael-hawker

UnitTests/UnitTests.UWP/UnitTests.UWP.csproj

@@ -18,7 +18,7 @@
     <ProjectTypeGuids>{A5A43C5B-DE2A-4C0C-9213-0A381AF9435A};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
     <UnitTestPlatformVersion Condition="'$(UnitTestPlatformVersion)' == ''">$(VisualStudioVersion)</UnitTestPlatformVersion>
     <AppxPackageSigningEnabled>false</AppxPackageSigningEnabled>
-    <LangVersion>8.0</LangVersion>
+    <LangVersion>9.0</LangVersion>
   </PropertyGroup>
   <Target Name="Pack">
   </Target>

UnitTests/UnitTests.UWP/VisualUITestBase.cs

@@ -24,19 +24,18 @@ public class VisualUITestBase
         /// </summary>
         /// <param name="content">Content to set in test app.</param>
         /// <returns>When UI is loaded.</returns>
-        protected Task<bool> SetTestContentAsync(FrameworkElement content, TaskCreationOptions? options = null)
+        protected Task SetTestContentAsync(FrameworkElement content)
         {
-            var taskCompletionSource = options.HasValue ? new TaskCompletionSource<bool>(options.Value)
-                : new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
-
-            App.DispatcherQueue.EnqueueAsync(() =>
+            return App.DispatcherQueue.EnqueueAsync(() =>
             {
+                var taskCompletionSource = new TaskCompletionSource<bool>();
+
                 async void Callback(object sender, RoutedEventArgs args)
                 {
                     content.Loaded -= Callback;
 
                     // Wait for first Render pass
-                    await CompositionTargetHelper.ExecuteAfterCompositionRenderingAsync(() => { }, TaskCreationOptions.RunContinuationsAsynchronously);
+                    await CompositionTargetHelper.ExecuteAfterCompositionRenderingAsync(() => { });
 
                     taskCompletionSource.SetResult(true);
                 }
@@ -53,35 +52,26 @@ async void Callback(object sender, RoutedEventArgs args)
                 {
                     taskCompletionSource.SetException(e);
                 }
-            });
 
-            return taskCompletionSource.Task;
+                return taskCompletionSource.Task;
+            });
         }
 
         [TestCleanup]
         public async Task Cleanup()
         {
             var taskCompletionSource = new TaskCompletionSource<bool>();
 
-            // Need to await TaskCompletionSource before Task
-            // See https://devblogs.microsoft.com/premier-developer/the-danger-of-taskcompletionsourcet-class/
-            await taskCompletionSource.Task;
-
             await App.DispatcherQueue.EnqueueAsync(() =>
             {
-                void Callback(object sender, RoutedEventArgs args)
-                {
-                    App.ContentRoot.Unloaded -= Callback;
-
-                    taskCompletionSource.SetResult(true);
-                }
-
                 // Going to wait for our original content to unload
-                App.ContentRoot.Unloaded += Callback;
+                App.ContentRoot.Unloaded += (_, _) => taskCompletionSource.SetResult(true);
 
                 // Trigger that now
                 App.ContentRoot = null;
             });
+
+            await taskCompletionSource.Task;
         }
     }
 }