This TechTalk explains how to easily test in an autonomous way an application conceived with modular abstractions such as the "layer". Acquire fundamental knowledge about how to partition into layers the concerns of the application. Learn the best practices regarding application architecture and modularity. See how to apply "top-down" as well as "test-driven" design techniques. Learn how to correctly design the "velcro", the visible interface of a module. In the same way, learn how to conceive a "fake" implementation, an efficient strategy to test a module in an autonomous way. Overall, you'll learn how to design for testability and why we need a unit of modularity that goes beyond object.