I once had a talk with Kent Beck way way back in the day (early 2000s) about how much unit tests there should be, etc... and I think its nicely captured by his reply here
A lot of people seem to miss many of Kent's subtly, but intentionally phrased advice. Unit Tests are a liability, so use them responsibly and as little as possible, but not at the expense of removing confidence in your software.
Also, delete tests that aren't doing you any favors.
Thanks for the link! I never knew that Kent Beck, one of the fathers of TDD, said such a thing already in 2008. And in the mean while herds of developers have started to chase goals like 90% test coverage, thinking that this is the way that guys like Kent Beck do TDD. If only they would have known earlier!
The problem is that to follow his advice you need judgement. From my experience more and more devs want strict self-imposed rules that need to be followed so they don't have to think.
http://stackoverflow.com/questions/153234/how-deep-are-your-...
A lot of people seem to miss many of Kent's subtly, but intentionally phrased advice. Unit Tests are a liability, so use them responsibly and as little as possible, but not at the expense of removing confidence in your software.
Also, delete tests that aren't doing you any favors.