ActionScript is the ScriptingLanguage used in MacromediaFlash. Because it is closely based on ECMAScript, it has many of the same strengths and weaknesses expressed in JavaScriptRocks and JavaScriptSucks.
Short history of ActionScript
There have been some efforts to build a TestingFramework for ActionScript (to be called AsUnit, of course), but so far nothing has come of it.
There is a Wiki devoted to ActionScript at http://chattyfig.figleaf.com/flashcoders-wiki/index.php
See http://www.actionscripts.org http://www.flashkit.com
There is now a rather nice TestingFramework for MacromediaFlash 7 (Flash MX Pro 2004) called AS2Unit. It is specifically designed for the above version of Flash since it includes project level functionality, source code control, etc.
It's fantastic to see the powerful (if poorly specified) ECMAScript language used outside of web design. Would that it were being used somewhere where it isn't specifically for the use of non-programmers, resulting in the same sort of crud:
for(i = 0; i < num_boxes; i++){ box = eval("root.myBox" + i); box.text = eval("boxText" + i); }