I once spent an evening reading and watching wise people on the internet to find out where is difference between unit tests and integration tests. It's really f

I once spent an evening reading and watching wise people on the internet to find out where is difference between unit tests and integration tests. It's really fuzzy and depends on a source. There's no agreement what is "unit". Few classes interacting with each other could still be a unit. I didn't find any strict definition which would be useful in practice. I just write tests and guess they are mostly integration tests, some end-to-end tests and a few unit tests.