Yes they do when you don't have an exact spec of what you're creating. That's been my experience anyway. Tests are great when: * You have the spec before writ

Yes they do when you don't have an exact spec of what you're creating. That's been my experience anyway. Tests are great when: * You have the spec before writing any code (not necessarily for the whole system, or even large parts of it). * You've settled on a design/implementation, and need to make sure you don't accidentally break it in future.