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POUnit Testing an Event Firing From a Thread
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  1. POUnit Testing an Event Firing From a Thread
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    copied!<p>I'm having a problem unit testing a class which fires events when a thread starts and finishes. A cut down version of the offending source is as follows:</p> <pre><code>public class ThreadRunner { private bool keepRunning; public event EventHandler Started; public event EventHandler Finished; public void StartThreadTest() { this.keepRunning = true; var thread = new Thread(new ThreadStart(this.LongRunningMethod)); thread.Start(); } public void FinishThreadTest() { this.keepRunning = false; } protected void OnStarted() { if (this.Started != null) this.Started(this, new EventArgs()); } protected void OnFinished() { if (this.Finished != null) this.Finished(this, new EventArgs()); } private void LongRunningMethod() { this.OnStarted(); while (this.keepRunning) Thread.Sleep(100); this.OnFinished(); } } </code></pre> <p>I then have a test to check that the <code>Finished</code> event fires after the <code>LongRunningMethod</code> has finished as follows:</p> <pre><code>[TestClass] public class ThreadRunnerTests { [TestMethod] public void CheckFinishedEventFiresTest() { var threadTest = new ThreadRunner(); bool finished = false; object locker = new object(); threadTest.Finished += delegate(object sender, EventArgs e) { lock (locker) { finished = true; Monitor.Pulse(locker); } }; threadTest.StartThreadTest(); threadTest.FinishThreadTest(); lock (locker) { Monitor.Wait(locker, 1000); Assert.IsTrue(finished); } } } </code></pre> <p>So the idea here being that the test will block for a maximum of one second - or until the <code>Finish</code> event is fired - before checking whether the <code>finished</code> flag is set.</p> <p>Clearly I've done something wrong as sometimes the test will pass, sometimes it won't. Debugging seems very difficult as well as the breakpoints I'd expect to be hit (the <code>OnFinished</code> method, for example) don't always seem to be.</p> <p>I'm assuming this is just my misunderstanding of the way threading works, so hopefully someone can enlighten me.</p>
 

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