I almost never write single function unit tests. There's usually some subset of the codebase that's self contained that makes sense to be the "unit" you're test

I almost never write single function unit tests. There's usually some subset of the codebase that's self contained that makes sense to be the "unit" you're testing, but it's almost always a handful of functions with a clear entry point. My general rule is to never mock or remove anything that has no side effects from the execution path of a test, even if it's some utility function that's already tested in isolation in its own test suite - trying to isolate every little bit of behaviour to be tested separately is just a bunch of extra work for questionable benefit. I still call these tests "unit tests", and I think a lot of people do also. But there are the dogmatic people to whom only a test covering a single function with all dependencies mocked out is a true unit test.