Depends. If the 'unit' is big enough to have an interface spec then a different dev should write the test. If you're doing function level unit testing, a dev

Depends. If the 'unit' is big enough to have an interface spec then a different dev should write the test. If you're doing function level unit testing, a dev should write it. There's a grey area between those two extremes. My original post was intended to focus on system and api level testing but I wasn't clear on that.