Comment by m12k

I disagree with the notion that making your code testable in isolation serves no other purpose than to write unit tests. It very specifically forces you to think about how and why each piece of code is coupled with other code, and generally requires you to make this coupling as loose as possible, to make testing in isolation possible. Loosely coupled code is also easier to reason about and easier to refactor. So testing doesn't just provide you with the value of tests, it also nudges you toward a saner architecture.