When you try to instantiate a windowsforms control in your NUnit test, you could get the following error:

System.Threading.ThreadStateException: Current thread must be set to single thread apartment (STA) mode before OLE calls can be made. Ensure that your Main function has STAThreadAttribute marked on it.

This has something to do with the fact that windows forms controls like to run in STA (Single threaded apartment) and the latests version of Nunit run as MTA (Multi Threaded apartment).

After some googling (which only returned a small number of hits), I found “Nunit and STATThread by frater”. The solution happens to be very simple. Add this to the assembly where you have the test and the error will go away.

So another day and another problem solved.

Let’s say we want to test to see if our object really throws that event when we need it to.

So when calling a method SomeSub an event throwme will be raised.

Now we make a little unittest class that looks like this.

Just a few notes. I created an interface just for this test. And interface with a method with the same signature as the event. Then in the Test, I subscribe the event to that method. I didn’t forget to set IgnoreArguments and I called the Method on our object.

If the test goes green, we know that the event is raised when we call the sub. Now it’s just a matter of subscribing to that event.