I agree you need some integration tests, but, in my experience, if you define an interface the defines what you need from third parties, you can make 90% of the

I agree you need some integration tests, but, in my experience, if you define an interface the defines what you need from third parties, you can make 90% of the code you care about unit testable. For me, this isn’t just theory: I’ve worked at a place that trained its employees to write code this way, and the benefit was obvious.