Day has been Unit Test cleanup day. My current project has over 1000 tests that cover about 2 years worth of code. I don't write tests for tests sake, so most of these tests are testing a fairly significant bug fix or feature that I've added. Since they test real things, they break when the real world changes. Usually the reason is because underlying data changed and the input data or the checked data needs to updated.

Once again, I had fun using regular expressions to turn brittle tests into robust tests. It's always satisfying when I have all my unit tests working and a release candidate deployed into beta.