> Testable code is not a good thing in and of itself. Code should only be testable at its high level interfaces i.e. interfaces that are close to the requiremen

> Testable code is not a good thing in and of itself. Code should only be testable at its high level interfaces i.e. interfaces that are close to the requirements. So if the code is a library then the high level interface may be the public interface of a class. Perhaps I misunderstand you, but I have to disagree with this. Testable code is absolutely a good thing in and of itself. When something breaks, being able to isolate each piece of the codebase and figure out why it's breaking is essential. Far too often I've got bug reports from other developers saying "System X is broken, what changed?". When I ask for more detail, a test case proving it's broken, etc - they can't come up with that. Their test case is "our entire service is broken and I think the last thing that happened was related to X". Sometimes it is a problem with System X, but more frequently it's something else in their application. The smaller you can make your test case, the better, and the easier it is to get a grasp of the acutal problem.