Except for the part where you refactor your code, which by definition shouldn't be changing its behaviour and therefore can't be driven by adding tests to your

Except for the part where you refactor your code, which by definition shouldn't be changing its behaviour and therefore can't be driven by adding tests to your test suite, where exactly the same design issues will immediately arise. By comparison to Smalltalk, most environments seem broken to a seasoned Smalltalker. The main refactoring tool in Smalltalk would happily refactor your tests, so you'd just do your refactoring and re-run the tests. No interference with any reasonable implementation of TDD needed at all. You just counted refactoring as writing the tests and then immediately ran the unit tests.