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POC# and Moq - How to Assert an Event is Not Raised
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  1. POC# and Moq - How to Assert an Event is Not Raised
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    copied!<p>I have an application that raises events depending on the state of a Sim object. In particular, if the state of the Sim changes - i.e. from PinRequired to Accessible - an OnStatus event will be raised. The events notify listeners on a new thread.</p> <p>I am using Moq in my unit tests and am able to assert that OnStatus is raised like so:</p> <pre><code> [Test] public void TestOnStatusIsRaised() { Sim sim = new Sim(); sim.OnStatus += OnStatus; lock (this) { sim.UpdateSimInfo(new Info("a new status")); Monitor.Wait(this); } Assert.IsTrue(_onStatusCalled); } private void OnStatus(SimStatus obj) { lock (this) { _onStatusCalled = true; Monitor.Pulse(this); } } </code></pre> <p>As you can see, using the Monitor class I can wait until the event is raised before proceeding and asserting that the _onStatusCalled flag has been set to true.</p> <p>My difficulty arises when I want to assert that an event is not raised. I can't use Monitor to wait for the event not to be raised as the test would wait forever! I could added a timeout to the wait, but that seems like a dirty hack.</p> <p>I have tried the following:</p> <pre><code> [Test] public void TestOnStatusIsNotFired() { Sim sim = new Sim(); sim.OnStatus += onStatus =&gt; Assert.Fail("OnStatus Was called"); sim.UpdateSimInfo(new Info("the same status")); } </code></pre> <p>but it doesn't work - before fixing the code to ensure the event is not raised, the test always passes. I have even stepped through the code and observed an exception being thrown by the <code>Assert.Fail()</code>, but this does not cause the test to fail as my event is raised in a try/catch block and the NUnit exception is caught.</p> <p>Any ideas?</p>
 

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