> However, if you’re still developing the interface definition itself, TDD just wastes time when it transpires the interface you envisaged and wrote tests for d

> However, if you’re still developing the interface definition itself, TDD just wastes time when it transpires the interface you envisaged and wrote tests for doesn’t quite match up with the implementation as you write it. This sounds like TDD is WAI in this case. If the tests break because of the implementation of the interface, either the tests were wrong (likely because the interface was poorly or incompletely described) or the requirements changed (and broken tests means you had decent coverage). Catching this with a simple test run during initial development is far cheaper than debugging against someone else's expectations in the future.