[antonovka2]

Unit tests are narrow and focused, and aimed at verifying features. What you're talking about is something I'd call white box QA. Which is valuable, though it's essentially just an extension of design, and has the same limits.

It seems like most negative arguments regarding "unit tests" start by defining them as a small subset of what can be usefully tested, and then arguing against the value of testing such an incomplete subset.

I don't see the point of drawing such an arbitrary line. I leverage "unit" tests to automatically test units of code as completely as possible (not just 'verify features'), and I expect the same of tests that others write.