Two new chapters fresh up on the Apress alpha books page:
Chapter 5 "Detailed Design and Unit Testing"
In DDT we make the distinction between unit testing - testing at the atomic level - and controller testing - testing at the molecular level. Chapter 5 shows how to drive "atomic-level" unit tests from a detailed UML design, identifying test cases and scenarios from key points in the design.
Chapter 6 "Conceptual Design and Controller Testing"
A conceptual design is the first foray into the design of a system, having produced use cases to describe the user/system interaction. The system behaviour is captured in "controllers" (logical software functions). Later, each controller will become one or more "real" functions/methods on your classes; but having identified these high-level functions at a conceptual level, why not write tests at this level as well? That's what controller testing is all about - it gives you more "bang for your buck", as you need to write fewer tests but they give you essentially the same feedback as micro-grained unit tests.
Whereas a unit test may be "concerned" with one software method, a controller test operates on a small group of closely related methods that together perform a useful function.