TDD can work if the tests are integration tests and each test case covers an entire feature (one which can be clearly described using non-technical language). I

TDD can work if the tests are integration tests and each test case covers an entire feature (one which can be clearly described using non-technical language). Integration tests only lock down the high level interfaces and behaviors so they allow you to keep reworking the guts of the system without ever having to rewrite the test cases. Unit tests are mostly only good in the very final stages of the project when you have a fully working, essentially perfect, bug-free system and you just want to lock it all down so that nobody can make even the tiniest changes to the code without breaking all the tests and becoming insecure about their abilities in the face of such a remarkable code base. If you're writing unit tests for poorly architected code, you're essentially locking down this horrible architecture and forcing all future developers to find complex ways to work around it instead of allowing them to confidently make the necessary restructurings to allow them to cleanly build on top (this kind of "I'm not breaking any features" confidence can only come from integration tests). When it comes to complex systems, writing unit tests too early in the project is a bad idea; especially when combined with an agile development methodology. It's like building a skyscraper over several years and perfectly analysing every steel rod, every brick and every pane of glass as it is added to the structure but never actually stepping back to check that the structure as a whole is actually pointing upwards.