Unit tests don't have to test everything... just the units. Integration tests should be testing the interactions between different modules. And system tests should be the whole stack top-to-bottom. It ends up looking like a pyramid.
Yes thank you I know the testing pyramid. But testing should concentrate on what adds value and a zillion unit tests, with everything mocked often don't. Infact they can be a distraction from the bigger picture. Rather than rules, methodologies etc. we should TWMS - Test What Makes Sense. Or even better TWAV - Test What Adds Value. Or DTFTS - Don't Test For Testings' Sake.
If I understood correctly I think that's what Uncle Bob was trying to argue for in this blog post.
I don't think having 3-4 tests per LOC is such a bad thing. Far more testing goes into the sqlite codebase and I think it'd be hard to argue that it could have been better if the developers had stopped wasting their time and concentrated on what added value.
