Test Driven Development in the Mobile World

When it's, you probably write your code first, and then write a couple of test cases that kind of prove that everything. Is that how you usually work? I've done it both ways. Most of the time it slows me down. But there are places where there are certain methods that are so critical. It's really nice to test every single combination. And if I discover something bad when I'm writing those tests, I really should go back and change the implementation.