To be fair to unit tests, I really like them for making sure that complicated code gets tested thoroughly. However, very often the complicated code isn't isola

To be fair to unit tests, I really like them for making sure that complicated code gets tested thoroughly. However, very often the complicated code isn't isolated to a single unit. It instead lives distributed amongst multiple objects that are reused for several competing aspects and all have their own undocumented assumptions about how the world works. Now maybe this implies that we need a wide scale change in coding methodology such that the complicated parts are all isolated to units. But pending that, I'm not sure that the answer is a bunch of static mocks pretending to be dynamic objects with yet another set of undocumented assumptions of how the world works. The unit tests that have made me happiest has been unit tests on top of a very complicated library that had a very simple api. And on the other hand, the tests that make me most believe that the projects I'm working on are correct have been integration tests incorporating a significant part of the application AND the QA team's test very thorough test plan.