public class AwaitForeachReproduction { public async Task<int> Execute(CancellationToken token) { int sum = 0; await foreach (int result in AsyncEnumerable(token)) { sum += result; } return sum; } private async IAsyncEnumerable<int> AsyncEnumerable([EnumeratorCancellation] CancellationToken cancellationToken) { for (int i = 0; i < 100; i++) { await Task.Delay(10, cancellationToken); yield return i; } } } 

public class AwaitForeachReproductionFixture { [Test] public async Task Execute_Should_Work() { // Arrange var sut = new AwaitForeachReproduction(); // Act var result = await sut.Execute(CancellationToken.None); // Assert Assert.AreEqual(result, 4950); } [Test] public void Execute_Should_Be_Canceled() { // Arrange var sut = new AwaitForeachReproduction(); var cts = new CancellationTokenSource(); // Act var resultAsync = sut.Execute(cts.Token); cts.Cancel(); // Assert Assert.ThrowsAsync<TaskCanceledException>(async () => await resultAsync); } }