To the best of my knowledge this is not possible due to the ant build, but there might be some way that I am just not familiar with.
If you are launching the tests in Flash Builder, they can be launched in debug mode and you can accomplish the behavior you mention. It is the ant component here that becomes the wild card.
Unfortunately, I have to use ant build to run my tests.
I wish I could just somehow get Flash Builder to use ant as it's native builder, but I guess I'm hoping for too much.
It is possible!
Flash Builder compiles swf in bin-debug folder for debugging. If you copy and override this file with the one you built using ant in your build process, Flash Builder will use that file instead.
Yep, that will work. good call.
Just make sure you don't build through builder/have build automatically on at any point or it will likely hose you up.