I’m not sure how I came across this article, I think maybe it was linked off the Google Reader blog, but Cedric has some interesting things to say about Test-Driven Development. I would just like to take issue with one small assertion of his:
Keep in mind that functional tests are the only tests that really matter to your users. Unit tests are just a convenience for you, the developer. A luxury. If you have time to write unit tests, great: they will save you time down the road when you need to track bugs. But if you don’t, make sure that your functional tests cover what your users expect from your product."
I can tell you from experience that having poor unit testing can make your functional testing a total nightmare because, in a sense, you may have good functional code working with bad “data”, in this case the unit code. Garbage in, garbage out, as was hammered into my head back in school. You can end up wasting more time, in this regard, and unit testing is no longer a thing of luxury, but something that could have saved you a few hours of head scratching.