There are some gray areas, sure. I usually find a way around making mocks, but maybe it's just the domains I am in. My biggest mistakes are mostly just writing

There are some gray areas, sure. I usually find a way around making mocks, but maybe it's just the domains I am in. My biggest mistakes are mostly just writing tests that are too intertwined with internal interfaces. So they break all the time and need to be adjusted when refactoring. That's a drag.