Test Driven Design really helps us learn about the design of our code and how to improve on it. It is also true that the more we know about design, the more our code can actually benefit from TDD. This talk will cover just enough to give you the design inspiration you need to appreciate TDD. We will see responsibility driven design, "Tell don't ask", the law of Demeter, Dependency Inversion and other very key design principles and how they change the way we look into coding and testing.