A while ago, Eric Shupps wrote about TDD and SharePoint development. His follow up post is really a good read, because rather concentrating on the technique (TDD or Test After), he’s concentrating on why we do unit tests in the first place: Making better code, for less bugs and shortening development cycles.
And I like this quote:
"In fact, I would argue that, due to the complexity of the SharePoint object model, the various undocumented and often erratic behaviors, and the level of skill required to effectively troubleshoot and optimize such code, Unit testing has more value in a SharePoint context than in any other.”
Yes, you can replace SharePoint with your favorite technology and it’s still works…