There are a few options, and which tool works for you depends on your specific circumstance, so heres a list of the ones I've seen used;


 * [FlexMonkey][1] - Provides an IDE recorder, test case exporting and can be integrated into CI tools such as Jenkins using its ANT tasks.
  * Pros: Creates FlexUnit test cases
  * Cons: Doesn't play well with custom components or very complex interfaces
 * [Sikuli][2] - Doesn't test Flash as such, but uses Image Recognition tech to recognise buttons/layout elements etc, and can control *any* application
  * Pros: Can interact on *anything* the user can see
  * Cons: Struggles with highly variable interfaces (dynamic backdrops, etc) and doesn't allow you to validate text very easily (ie you can't do things like; assertThat(page.getTitle(), is(equalTo("Some Expected Title")));
 * flash-selenium - An extension to the very popular Selenium test system
  * Pros : Lets you maintain a common work flow if you're using Flash within other html content
  * Cons : Requires building a Selenium version of the flash application


  [1]: http://flexmonkey.gorillalogic.com/
  [2]: http://www.sikuli.org/