[wilhelm]

For web applications? Watir. Unit tests are great and all, but not that useful compared to high-level functional tests that tests the stuff users are actually interested in doing. With limited time and limited resources, write Watir tests first.

Test #1: Sign up. Did it work? Were all parameters set correctly? Test #2: Log in. Did it work? Are you logged in as the correct user? Test #3: Something that touches your most important business logic. Can the logged in user add an item to her shopping cart? Post in her blog?

Just a hundred tests like that gets you a long way, and doesn't take that long to write.