>design feedback that integration or acceptance style tests won't give you. That "feedback" is the pain you feel when you have to maintain one form of tight co

>design feedback that integration or acceptance style tests won't give you. That "feedback" is the pain you feel when you have to maintain one form of tight coupling (ordinary bad code) combined with another (micro-level unit tests). Higher level tests won't cause you that 'guiding pain' because they aren't as tightly coupled to your implementation. IMO you don't need to write tens of thousands of lines of unit test code to spot that you're building tight coupling in. It's something you can spot simply by knowing what to look for. Moreover, if you make a design mistake or introduce tech debt lower down the stack, having a panoply of low level unit tests means that refactoring will break those tests even if you haven't introduced any bugs. IME that causes a dangerous cementing effect on bad code. I think if you've got a module which is self contained, reusable and tightly scoped, it's worth surrounding with a lower level test. But, if you don't, you're doing more harm than good by surrounding a module with tests.