fix flaky tests

src/Samples/TestStack.BDDfy.Samples/CanRunAsyncSteps.cs

@@ -7,7 +7,7 @@ namespace TestStack.BDDfy.Samples
 {
     public class CanRunAsyncSteps
     {
-        private Sut _sut;
+        private object _sut;
 
         internal async void GivenSomeAsyncSetup()
         {
@@ -25,23 +25,19 @@ internal async void AndThenBddfyShouldCaptureExceptionsThrownInAsyncMethod()
             throw new Exception("Exception in async void method!!");
         }
 
-        private async Task<Sut> CreateSut()
+        private static async Task<object> CreateSut()
         {
             await Task.Delay(500);
-            return new Sut();
+            return new object();
         }
 
         [Fact]
         public void Run()
         {
             var engine = this.LazyBDDfy();
-            var exception = Should.Throw<Exception>(() => engine.Run());
+            var exception = Should.Throw<Exception>(engine.Run);
 
             exception.Message.ShouldBe("Exception in async void method!!");
         }
-
-        internal class Sut
-        {
-        }
     }
 }

src/TestStack.BDDfy/Processors/AsyncTestSyncContext.cs

@@ -8,21 +8,26 @@ namespace TestStack.BDDfy
     /// </summary>
     internal class AsyncTestSyncContext : SynchronizationContext
     {
-        readonly ManualResetEvent _event = new(initialState: true);
+        readonly object _lock = new();
         Exception _exception;
         int _operationCount;
 
         public override void OperationCompleted()
         {
-            var result = Interlocked.Decrement(ref _operationCount);
-            if (result == 0)
-                _event.Set();
+            lock (_lock)
+            {
+                _operationCount--;
+                if (_operationCount == 0)
+                    Monitor.PulseAll(_lock);
+            }
         }
 
         public override void OperationStarted()
         {
-            Interlocked.Increment(ref _operationCount);
-            _event.Reset();
+            lock (_lock)
+            {
+                _operationCount++;
+            }
         }
 
         public override void Post(SendOrPostCallback d, object state)
@@ -59,7 +64,12 @@ public override void Send(SendOrPostCallback d, object state)
 
         public Exception WaitForCompletion()
         {
-            _event.WaitOne();
+            lock (_lock)
+            {
+                while (_operationCount > 0)
+                    Monitor.Wait(_lock);
+            }
+
             return _exception;
         }
     }