I'm really impressed with unit testing. If you think of your program like a building, the unit tests are the scaffolding. I'd used similar stuff before but then I'd throw the small tests away. Bite size pieces of code to make sure everything was working. With unit tests each test confirms that you're code's working and going the way you want to it to.
Anyway I was so impressed I decided to sign up to the nunit mailing list and see what useful tit-bits I could glean.
I'm working on quite a tricky library at the moment and trying to make it modular - at least for now (if it's too hard, or there are too many casts later - I'll merge it).
I'm working tomorrow :( So no game programming. I'm hoping on monday I finally be able to finish off stage two. It's a lot of code but I'm optimistic. I'm also tempted to start making some of my code unit tested but I think I'll resist such a urge for now.