There has been a lot of fuzz around the topic of test-driven development; some find it useful; some don't see any value in it. You also have different flavours like Detroit being inside-out, or London going from the outside-in. And then you have people saying TDD is about testing or is it a design tool? In this session, we will talk with Dave Farley about all these topics, and especially how to use TDD as a design tool. Dave Farley is well known in the software community, especially being the co-author of the continuous delivery book. He is also a firm believer that Test-driven development is one of the core principles to do proper continuous delivery.