We need high-level integration tests and low-level unit tests – the trees and the leaves. We need integration tests to test user stories front to back, including calls to external dependencies. And we need unit tests to give ourselves a chance at getting complete coverage of a system’s functionality.

It’s a joy to work on a well-tested codebase and make changes without worrying about breaking things. The more I use unit tests, the more benefits I find. There’s the obvious benefit of preventing regressions, but there are so many more