FlexMojos isn't quite stable plus we can't upgrade to Maven 3 for various reasons. We ended up just compiling the classes to includes. Below is an example.
<fileset id="test.src.loc.fileset" dir="${test.src.loc}">
<include name="/Test*.as" />
<include name="/*TestCase.as" />
</fileset>
<path id="test.src.loc.path">
<pathelement location="${test.src.loc}"/>
</path>
<property name="test.src.loc.path" refid="test.src.loc.path"/>
<pathconvert pathsep="; import " property="test.runner.imports" refid="test.src.loc.fileset">
<chainedmapper>
<globmapper from="${test.src.loc.path}\" to=""/>
<packagemapper from=".as" to=""/>
</chainedmapper>
</pathconvert>
<pathconvert pathsep=", " property="test.runner.calls" refid="test.src.loc.fileset">
<chainedmapper>
<globmapper from="${test.src.loc.path}\" to=""/>
<packagemapper from=".as" to=""/>
</chainedmapper>
</pathconvert>
<copy tofile="${test.runner}" file="${test.runner.template}" overwrite="true" />
<replace file="${test.runner}" token="#IMPORTS#" value="${test.runner.imports}" />
<replace file="${test.runner}" token="#CALLS#" value="${test.runner.calls}" />
<fileset id="main.src.loc.fileset" dir="${main.src.loc}">
<include name="com/classes//*.as" />
<exclude name="com/other/classes/" />
</fileset>
<path id="main.src.loc.path">
<pathelement location="${main.src.loc}"/>
</path>
<property name="main.src.loc.path" refid="main.src.loc.path"/>
<pathconvert pathsep=" " property="main.src.loc.classes" refid="main.src.loc.fileset">
<chainedmapper>
<globmapper from="${main.src.loc.path}\" to=""/>
<packagemapper from=".as" to=""/>
</chainedmapper>
</pathconvert>
<fileset id="library.path" dir="${basedir}">
<include name="${flexcover.framework.loc}/frameworks/libs/*.swc" />
<include name="${flexcover.framework.loc}/frameworks/locale/en_US/.swc" />
<include name="${unit.test.lib.loc}/.swc" />
<include name="${lib.loc}/*.swc" />
</fileset>
<pathconvert pathsep=" " property="library.path" refid="library.path"/>
<exec executable="${mxmlc.exe}" dir="${main.src.loc}">
<arg line="${test.runner}" />
<arg line="-output ${test.finalName}" />
<arg line="-source-path ${main.src.loc} ${test.src.loc} ${main.src.loc}/../locale/en_US ${test.src.loc}/../resources" />
<arg line="-library-path ${library.path}" />
<arg line="-locale en_US" />
<arg line="-includes ${main.src.loc.classes}" />
<arg line="-verbose-stacktraces=true" />
</exec>