In order to get stated with building FLEX application with Maven, please visit: https://cwiki.apache.org/confluence/display/FLEX/Preparing+FDKs+for+Maven+builds
Not all resources needed by the build are available via Maven. Adobe has been quite restrictive with some of its resources.
We have therefore developed a Maven extension that should hide all the trouble of getting your environment setup. As this has not yet been released, you have to build it, but it shouldn't be that hard to do.
One thing you do need though in addition to this in order to run the Flex unit-tests, is a working flashplayer binary in your PATH.