@@ -24,6 +24,11 @@ namespace Tvl.VisualStudio.MouseFastScroll.IntegrationTests.Threading
2424 /// </summary>
2525 public sealed class WpfTestRunner : XunitTestRunner
2626 {
27+ /// <summary>
28+ /// A long timeout used to avoid hangs in tests, where a test failure manifests as an operation never occurring.
29+ /// </summary>
30+ private static readonly TimeSpan HangMitigatingTimeout = TimeSpan . FromMinutes ( 1 ) ;
31+
2732 public WpfTestRunner (
2833 WpfTestSharedData sharedData ,
2934 ITest test ,
@@ -46,34 +51,72 @@ public WpfTestRunner(
4651 protected override Task < decimal > InvokeTestMethodAsync ( ExceptionAggregator aggregator )
4752 {
4853 SharedData . ExecutingTest ( TestMethod ) ;
49- var sta = StaTaskScheduler . DefaultSta ;
54+
55+ DispatcherSynchronizationContext synchronizationContext = null ;
56+ Dispatcher dispatcher = null ;
57+ Thread staThread ;
58+ using ( var staThreadStartedEvent = new ManualResetEventSlim ( initialState : false ) )
59+ {
60+ staThread = new Thread ( ( ThreadStart ) ( ( ) =>
61+ {
62+ // All WPF Tests need a DispatcherSynchronizationContext and we don't want to block pending keyboard
63+ // or mouse input from the user. So use background priority which is a single level below user input.
64+ synchronizationContext = new DispatcherSynchronizationContext ( ) ;
65+ dispatcher = Dispatcher . CurrentDispatcher ;
66+
67+ // xUnit creates its own synchronization context and wraps any existing context so that messages are
68+ // still pumped as necessary. So we are safe setting it here, where we are not safe setting it in test.
69+ SynchronizationContext . SetSynchronizationContext ( synchronizationContext ) ;
70+
71+ staThreadStartedEvent . Set ( ) ;
72+
73+ Dispatcher . Run ( ) ;
74+ } ) ) ;
75+
76+ staThread . Name = $ "{ nameof ( WpfTestRunner ) } { TestMethod . Name } ";
77+ staThread . SetApartmentState ( ApartmentState . STA ) ;
78+ staThread . Start ( ) ;
79+
80+ staThreadStartedEvent . Wait ( ) ;
81+ Debug . Assert ( synchronizationContext != null , "Assertion failed: synchronizationContext != null" ) ;
82+ }
83+
84+ var taskScheduler = new SynchronizationContextTaskScheduler ( synchronizationContext ) ;
5085 var task = Task . Factory . StartNew (
5186 async ( ) =>
5287 {
53- Debug . Assert ( sta . StaThread == Thread . CurrentThread , "Assertion failed: sta.StaThread == Thread.CurrentThread " ) ;
88+ Debug . Assert ( SynchronizationContext . Current is DispatcherSynchronizationContext , "Assertion failed: SynchronizationContext.Current is DispatcherSynchronizationContext " ) ;
5489
5590 using ( await SharedData . TestSerializationGate . DisposableWaitAsync ( CancellationToken . None ) )
5691 {
57- try
58- {
59- Debug . Assert ( SynchronizationContext . Current is DispatcherSynchronizationContext , "Assertion failed: SynchronizationContext.Current is DispatcherSynchronizationContext" ) ;
60-
61- // Just call back into the normal xUnit dispatch process now that we are on an STA Thread with no synchronization context.
62- var invoker = new XunitTestInvoker ( Test , MessageBus , TestClass , ConstructorArguments , TestMethod , TestMethodArguments , BeforeAfterAttributes , aggregator , CancellationTokenSource ) ;
63- return invoker . RunAsync ( ) . JoinUsingDispatcher ( CancellationTokenSource . Token ) ;
64- }
65- finally
66- {
67- // Cleanup the synchronization context even if the test is failing exceptionally
68- SynchronizationContext . SetSynchronizationContext ( null ) ;
69- }
92+ // Just call back into the normal xUnit dispatch process now that we are on an STA Thread with no synchronization context.
93+ var invoker = new XunitTestInvoker ( Test , MessageBus , TestClass , ConstructorArguments , TestMethod , TestMethodArguments , BeforeAfterAttributes , aggregator , CancellationTokenSource ) ;
94+ return await invoker . RunAsync ( ) ;
7095 }
7196 } ,
7297 CancellationTokenSource . Token ,
7398 TaskCreationOptions . None ,
74- new SynchronizationContextTaskScheduler ( sta . DispatcherSynchronizationContext ) ) ;
99+ taskScheduler ) . Unwrap ( ) ;
100+
101+ return Task . Run (
102+ async ( ) =>
103+ {
104+ try
105+ {
106+ return await task . ConfigureAwait ( false ) ;
107+ }
108+ finally
109+ {
110+ // Make sure to shut down the dispatcher. Certain framework types listed for the dispatcher
111+ // shutdown to perform cleanup actions. In the absence of an explicit shutdown, these actions
112+ // are delayed and run during AppDomain or process shutdown, where they can lead to crashes of
113+ // the test process.
114+ dispatcher . InvokeShutdown ( ) ;
75115
76- return task . Unwrap ( ) ;
116+ // Join the STA thread, which ensures shutdown is complete.
117+ staThread . Join ( HangMitigatingTimeout ) ;
118+ }
119+ } ) ;
77120 }
78121 }
79122}
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