[lucisferre]

This has been my experience as well. It is far more useful to test scenarios, which generally involves some amount of integration. This also ensures the most important level of decoupling, that of the test from the system. The author's approach to TDD results in tests that are heavily coupled to implementation. This may be fine during design but they become a huge liability over the long run.

My experience is that automated testing should test the system not the implementation.