You haven't answered "How else are you "unit testing every single function and method"?"
Given a medium-sized project and at least a passing and a failing test case for each function and method, you end up if not with hundreds, but with dozens of tests largely doing the same thing.
> We do have some integration test, of course. But it's a small part of the total test suite.
So what does your test suite contain? Lots of unit tests for each method and function. What else?