Flash Builder 4 (Premium)
FlexUnit should be installed by default in Flash Builder 4.
You can automatically create test case files in Flash Builder:
After creating at least one test function, you can run the FlexUnit tests:
You can choose which tests, theories, or suites to run in this window:
Flash Builder will automatically create a FlexUnitApplication.mxml file, when it runs, it will show an output like the following: