Personally, I think one QA person on dev team, which the dev can discuss test plans before writing code/tests is really useful. The QA person will always come up with test cases the dev wouldn't come up with and together you have a solid basis to start the work and write the appropriate tests. I really enjoyed working that way. The dev also learns over time what to consider when doing new work. Especially, when the QA is a subject matter expert (e.g. forex etc) and you not.