As a developper I don't like to do tests that much. Knowing that someone has the ability to achieve this is a relief. What I say is that there may be a need for test developpers. Not every organisation around has the money/time to have a position dedicated to this. Testing is includes code review & QA which means some knowledge of the codebase as such I would be glad if I could share on more subjects than just test code with people that do tests, like architecture, API design and project knowledge in general and become a technical referrer just like documentation is, when it exists.