While it doesn't alleviate the problems entirely, you can also run things like mutation tests that check that your unit tests actually test conditions, rather than just execute all the code.
I've written an depressingly high quantity of code in my career that blows up literally the first time it runs. I'd much rather that happen in a unit test than in production.
Any test that exercises a given branch is better than nothing.
> Any test that exercises a given branch is better than nothing.
I disagree with this. If you have a test that doesn't actually test anything, you can't tell that you're not really testing that branch. No test is better than a bad test because it's easier to fix.