Thank you SJT, for your helpful input.

In terms of integrating with external programs, about the best you can do without scripting is to just launch the applications.
Simply launching them is probably enough for now. If I build it correctly, I can also generate the illusion that it is all one integrated suite.

In general, integrating external apps with Flash in a nice way is difficult; there isn't really much system integration as far as Flash goes. If you know Director at all, you might be better off going that route.
I sincerely do not enjoy working with Director, (I had to in the past) but I guess you're right that it is probably slightly more suited for this project.

I'll try to get he basic functionality out of flash first, then maybe switch if it doesn't work. It might not even be necessary to be able to exactly send data to and from external programs.
The only thing that probably needs to get in, is a flag that sets wether a test is run or not.

I am very open to ideas about what I can do in terms of testing, so if anyone has a good idea, it will be more than welcome.