I really hate the projects I work on where they've overtested to the point of meaninglessness. Like every single class has a full suite of tests mocking every single dependency and it's impossible to look at it without breaking 50 test cases.

Similarly I hate the projects with no tests because I can't change anything and be sure I've not broken some use-case I didn't think about.

Much prefer the middle ground with modular, loosely coupled code and just enough tests to cover all the use cases without needing to mock every single little thing. It should be possible to refactor without breaking tests.