Most developers thing that Test-driven development (TDD) is about testing, but testing is only a small benefit from using TDD techniques. This session demonstrates how stringent TDD improves the structure of your code. I discuss TDD as a technique for vetting consumer calls, using mock objects to understand complex interactions between collaborators, and some discussions of improved code metrics yielded by TDD. This session shows that TDD is much more than testing: it fundamentally makes your code better at multiple levels.