Depending on the language you're using, there might be some tools to help you. For example, MS recently released a library for Design by Contract (aka Contract

Depending on the language you're using, there might be some tools to help you. For example, MS recently released a library for Design by Contract (aka Contract Programming) in .NET 4.0. It allows you to specify constraints on your methods, such as things you expect to be true before the method is called, after, and between all method calls in a class. The library is capable of static verification, but it's partly an experimental feature and you need to pay for expensive version of VS. (Runtime checking is available for free.) But, here is the cool part: MS also released an automatic test generator called PEX. It can do exactly what you've described - go into your code and automatically find edge cases, and generate tests that cover each of them. And it's free. So, you can write contracts, run PEX, and if something goes wrong, you will see which inputs generated exceptions. D also has DbC functionality. I don't think it runs any static verification on it yet, but you can use it to detect abnormalities during functional testing.