>> There are functional tests that exercise these classes working together. Fixing a bug in one class breaks many functional tests .. > Huh? If fixing a bug br

>> There are functional tests that exercise these classes working together. Fixing a bug in one class breaks many functional tests .. > Huh? If fixing a bug breaks a functional test, then either the test was correct and you changed your expected system behavior and the test saved your bacon, or the test was a change detector test not a functional test. I think it's more a symptom of fragile mocking, or just making a unit too small. IMO, when I was in that situation it was because the mocking framework was too fragile. In hindsight, it may have been useful to just have a library of hand-written mock classes instead of relying on a framework to do it for us.