Just dropping in 2 cents. While I too use FlexUnit and think that a consensus would be good on how to write tests, my fear is that we shouldn't say "use this one".
There are other contributors to Flex, such as ASUnit, that we would be snubbing. Sadly I feel the best solution is just let people write the tests and whatever they choose to use that is up to them. If a group of individuals want to all write using one version that is up to them, but I don't know about saying that one is the supported or only choice. -- Jonathan Campos