However if you test too much of your "internal" code, you just end up cementing the currently implemented logic. I often see tests that are basically checking

However if you test too much of your "internal" code, you just end up cementing the currently implemented logic. I often see tests that are basically checking if the code didn't change. I.e. checking if function calls (on injected (mock) objects) have been done in the exact specific order, instead of checking for some correct end result.