Transitioning is a Team Activity
Once you know what "done" means for a story, and the whole team is committed to getting a story to done, you can create an environment in which the test team can transition to agile. As long as the developers assist with testing frameworks, the business analysts assist with refining the story, and the testers assist with providing information about the product under test, the cross-functional project team can transition to agile.
Transitioning to agile is a cross-functional project team activity, not something just the developers do. If you have testers who can’t "keep up," it’s not the test team’s problem. It’s the project team’s problem. Fix it with the project team. Even if you start with just-barely-good-enough test frameworks, you can refactor them into something wonderful. You’ll find that testers will keep up with the developers.