In short: You don't. At least, not in quite the way that the orthodox expansion of TDD implies. I've found that TDD with a reading of "Testability-Driven Desig

In short: You don't. At least, not in quite the way that the orthodox expansion of TDD implies. I've found that TDD with a reading of "Testability-Driven Design" was useful for driving adoption of certain architectural patterns that made my software more easily testable. That, in turn, informed how I authored my APIs. And so on.