> yet no one seems to agree with me that devs should not write their own tests. Change Request (or whatever you call it in your flavor of agile) is the source

> yet no one seems to agree with me that devs should not write their own tests. Change Request (or whatever you call it in your flavor of agile) is the source informal description of behavior, while Specification, Code and Tests are three distinct formal descriptions of the same. If any of those three are written down by the same person, assumptions and thinking errors translate to the other largely defeating the very purpose of writing down another formal description in the first place. Unit tests became mainstream with proliferation of weak-dynamic languages (JS, Python) and concepts like TDD largely became mainstream due to lack of formal interface specification capabilities in the languages themselves. Stricter languages (Java, C++) cover huge portions of the testing in the type system. Tests written by the developer are okay if they are used as a substitute for a formal type system. However, tests intended to catch logic errors will contain the very same logic errors found in the code and such tests will only give you false confidence. It does not mean that tests must be written by a dedicated QA, but rather that tests should be written by a different person for them to serve the purpose they are intended to serve.