Luke Bayes in FlashCoders mailing list said:
“I’m elated to announce the alpha release of AsUnit 3.0! This build has been
completely rebuilt from the ground up using the JUnit sources, and provides
complete support for ActionScript 3.0!”

AsUnit 3.0.1 alpha is available for download

The guys from http://www.kugelfunk.de has built MTASC GUI to make easier for flash developer compiler thier AS 2.0.
This utility provides a graphical user interface (”GUI”) for Windows for the MTASC ActionScript Compiler from Motion Twin. It also lets you choose among FlashPlayer versions 6, 7, or 8 for immediate preview.
Features:

• Select files per drag & drop
• configure all MTASC options by mouse click
• open SWF files in FlashPlayer 6, 7, or 8 for comparison
• Launch Bar window for MTASC and preview which will always stay on top of other applications
• All settings will be saved automatically when app is closed (e.g. window positions)
• This app can also be launched from within another program (e.g. Action Script editor) for immediate MTASC compilation and preview

(e.g. In SEPY: Menu Tools -> Settings -> Tools -> “new entry”. Add path to this app, leave arguments blank. You can then assign a key command for this program in Tools -> Key Commands.

Download Version 1.0 - 4.10.2005