You can get the Flex 4 SDK at:
http://opensource.adobe.com/wiki/display/flexsdk/Download+Flex+4

Flex 4 SDK is assumed to be installed in $FLEX_ROOT

To compile and run the test suite run:

./tests

Run "./tests --help" inside tests/ to see scripts usage.

Compiling tests manually inside the tests/ directory:
$FLEX_ROOT/bin/mxmlc -static-link-runtime-shared-libraries -compiler.omit-trace-statements=false test.mxml -output test.swf

Creating new testcases
----------------------

Use template.mxml as a template for new testcases.

We've provided a simple Tests class which should be used where
possible to test general behaviour of AS classes. See Tests.as for its
usage.

Please use a naming scheme as follow:

For toplevel classes: tests/CLASSNAME_test.mxml (CLASSNAME is the
exact name of the class/function)

For other classes: tests/NAMESPACE_CLASSNAME_test.mxml (NAMESPACE is
for example "net" for "flash.net" classes/functions, e.g.:
tests/net_NetStream_test.mxml)

Please group all tests for one class in one file.

Subdirectories
--------------

tests/other:

Tests that aren't suitable for testing with the Tests class should be
put in here. (e.g.: testing video playing, StageScaleMode testing
etc...). The naming schemes still apply to these testcases though.

tests/unimplemented:

Tests for unimplemented features.

tests/performance:

Tests aimed at measuring runtime performance.