[Fact]
public async Task Dispose_Waits_On_Pending_Enqueue_Calls()
{
    var implResetEvent = new ManualResetEvent(false);
    var implMock = new Mock<TaskQueue.ITaskQueueImpl>();

    implMock.Setup(impl => impl.Enqueue(It.IsAny<Task>()))
        .Callback(() => implResetEvent.WaitOne());

    var delay = TimeSpan.FromSeconds(1);
    var queue = new TaskQueue(implMock.Object);

    var enqueueCompletionSource = new TaskCompletionSource<object>();
    var enqueueTask = Task.Run(
        () => queue.Enqueue(enqueueCompletionSource.Task));

    await Assert.ThrowsAsync<TimeoutException>(
        () => enqueueTask.TimeoutAfter(delay));

    var disposeTask = queue.DisposeAsync();

    await Assert.ThrowsAsync<TimeoutException>(
        () => disposeTask.TimeoutAfter(delay));

    implResetEvent.Set();

    await enqueueTask.TimeoutAfter(delay);
    await disposeTask.TimeoutAfter(delay);
}