This is why I like using a randomized framework such as QuickCheck (or its derivatives in non-Haskell languages, such as Java) along with typical unit testing.

This is why I like using a randomized framework such as QuickCheck (or its derivatives in non-Haskell languages, such as Java) along with typical unit testing. It's often easier to write than tedious unit tests, and it can catch a lot of funny corner cases you don't even think to test. Of course, this still isn't a guarantee. But it does make me feel better about my code.