Simon Willison’s Weblog

I’ve heard managers and teams mandating 100% code coverage for applications. That’s a really bad idea. The problem is that you get diminishing returns on our tests as the coverage increases much beyond 70% (I made that number up… no science there). Why is that? Well, when you strive for 100% all the time, you find yourself spending time testing things that really don’t need to be tested. Things that really have no logic in them at all (so any bugs could be caught by ESLint and Flow). Maintaining tests like this actually really slow you and your team down.

— Kent C. Dodds