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copied!<p>You can avoid the extra abstraction if you are willing to trade it for a small amount of view model pollution (i.e. introducing code that is only used for the sake of your tests) as follows:</p> <p>First add an optional AutoResetEvent (or ManualResetEvent) to your view model constructor and make sure that you "set" this AutoResetEvent instance when your background worker finishes the "RunWorkerCompleted" handler.</p> <pre><code>public class MyViewModel { private readonly BackgroundWorker _bgWorker; private readonly AutoResetEvent _bgWorkerWaitHandle; public MyViewModel(AutoResetEvent bgWorkerWaitHandle = null) { _bgWorkerWaitHandle = bgWorkerWaitHandle; _bgWorker = new BackgroundWorker(); _bgWorker.DoWork += (sender, e) => { //Do your work }; _bgworker.RunWorkerCompleted += (sender, e) => { //Configure view model with results if (_bgWorkerWaitHandle != null) { _bgWorkerWaitHandle.Set(); } }; _bgWorker.RunWorkerAsync(); } } </code></pre> <p>Now you can pass in an instance as part of your unit test.</p> <pre><code>[Test] public void Can_Create_View_Model() { var bgWorkerWaitHandle = new AutoResetEvent(false); //Make sure it starts off non-signaled var viewModel = new MyViewModel(bgWorkerWaitHandle); var didReceiveSignal = bgWorkerWaitHandle.WaitOne(TimeSpan.FromSeconds(5)); Assert.IsTrue(didReceiveSignal, "The test timed out waiting for the background worker to complete."); //Any other test assertions } </code></pre> <p>This is precisely what the AutoResetEvent (and ManualResetEvent) classes were designed for. So aside from the slight view model code pollution, I think this solution is quite neat.</p>

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