Task.Delay() not behaving as expected

Task.Delay returns a Task object on which you have to wait. Otherwise the following code will be executed immediately. Therfore you have to declare your method as async. Then you can await Task.Delay

public async Task ChattyWriter()
{
    int count = 0;
    while (true)
    {
        var message = String.Format("Chatty Writer number {0}", count);
        Trace.WriteLine(message);
        count++;
        await Task.Delay(1000);
           ...
    }
}

You have to interrupt your calling thread somehow. The unit test would terminate and the background thread as well. But if you call this method from the UI, the UI will not get blocked.

By calling Wait on an asynchronous method you will end up with a deadlock. See here for more information.