I wanted to point this out for people who say "the code is too complex for a unit test to verify," Don't kid yourself, you have written some really bad code.

Good code design is easy to implement and easy to test. If your code is too complicated to do this easily then you have going to have bugs and probalbly can point the finger at a bad design.

If you are having problems written simple tests, then you need to think about how your code works and make it easier to write and understand.