I think most of you guys missed the point. Writing tests is very important WHILE writing code, to write it better. We MUST write tests not only to catch regressions, to be sure that certain invariants will be manteined. But we write tests to check if we are writing good code. I need to write a class to do some stuff. The test is the first user of this class. If I cannot write the test very fast, and I see that I'm spending a lot of time doing it, this means that my class is poorly designed, is not flexible, is not very reusable. Maybe I'm doing something wrong with my app design. If I'm writing good code, reusable and clean code, testing is easy and fast. Testing help me to check immediately what's going wrong with the code, not only in term of bugs.