Regarding code samples, indeed, I illustrate this in all my training, but broadly speaking, I don't try to write _exhaustive_ integrated tests. I treat them more like smoke tests (if I'm writing them for programmers) or acceptance tests (if I'm writing them for customers). I merely mean that I don't rely on them to check basic correctness of behavior that can reasonably run without expensive external resources. (That's why we have interfaces/protocols.)