Question

I have code very similar to this but cannot work out how I test whether an event handler occured.

public class MyClass : MyAbstractClass
{ 
  IFileSystem FileSystem;

  public MyClass(IFileSystem myFileSys)
  {
    FileSystem = myFileSys;
    FileSystem.EventHit += new EventHandler(FileSystem_EventHit);
  }

  public void FileSystem_EventHit(object sender, EventArgs e)
  {
    //Testing base.OnOutput is not possible which I wont go into
    base.OnOutput("EventHit");
  }
}

Testing code is here:

    [Test]
    public void DoSomething_WhenCalled_EventFired()
    {
         var mock = new Moq.Mock<IFileSystem>();

         MyClass plugin = new MyClass (mock.Object);

         mock.Object.DoSomething();

         mock.Raise(x => x.EventHit += null, new EventArgs());

        //Verify/Assert that MyClass handled and did something in the event handler

    }

Answer 1

As verifying something in the event handler would mean trying to test legacy code the option I went with was to test that the event fired from within the concrete type and not a mock.

[Test]
public void DoSomething_WhenCalled_EventFired()
{

  FileSystem fs = new FileSystem(mock.Object, timerMock.Object);

  bool WasItHit = false;
  fs.EventHit += delegate { WasItHit = true; };

  fs.DoSomething(); //This should call the event

  Assert.IsTrue(WasItHit);
}