How does one unit test sections of code that are procedural or event-based

Question

I'm convinced from this presentation and other commentary here on the site that I need to learn to Unit Test. I also realize that there have been many questions about what unit testing is here. Each time I go to consider how it should be done in the application I am currently working on, I walk away confused. It is a xulrunner application application, and a lot of the logic is event-based - when a user clicks here, this action takes place.

Often the examples I see for testing are testing classes - they instantiate an object, give it mock data, then check the properties of the object afterward. That makes sense to me - but what about the non-object-oriented pieces?

This guy mentioned that GUI-based unit testing is difficult in most any testing framework, maybe that's the problem. The presentation linked above mentions that each test should only touch one class, one method at a time. That seems to rule out what I'm trying to do.

So the question - how does one unit testing procedural or event-based code? Provide a link to good documentation, or explain it yourself.

On a side note, I also have a challenge of not having found a testing framework that is set up to test xulrunner apps - it seems that the tools just aren't developed yet. I imagine this is more peripheral than my understanding the concepts, writing testable code, applying unit testing.

Answer 1

The idea of unit testing is to test small sections of code with each test. In an event based system, one form of unit testing you could do, would be to test how your event handlers respond to various events. So your unit test might set an aspect of your program into a specific state, then call the event listener method directly, and finally test the subsequent state of of your program.

If you plan on unit testing an event-based system, you will make your life a lot easier for yourself if you use the dependency injection pattern and ideally would go the whole way and use inversion of control (see http://martinfowler.com/articles/injection.html and http://msdn.microsoft.com/en-us/library/aa973811.aspx for details of these patterns)

(thanks to pc1oad1etter for pointing out I'd messed up the links)