Cannot test Play application with junit because of actors

since my (small) team started using actors in Play!, we get this nice error message each time we want to unit-test our application. FYI, the application is being developed in Java.

[error] Test utils.JsonUtilsTest.testBuildingJsonResponseWithPermissionsThrowsNullPointerException failed: java.lang.IllegalStateException: cannot create children while terminating or terminated, took 0.48 sec
[error]     at akka.actor.dungeon.Children$class.makeChild(Children.scala:266)
... 
[error]     at Global.startActors(Global.java:1248)

so let's take a look at the startActors method :

private void startActors() {
    ActorRef measureFrequencyMaster = RemoteActorsUtils.getInstance().getSystem()
                   .actorOf(Props.create(MeasureFrequencyMaster.class), "MeasureFrequencyMaster");
    BatchMessage msg = new BatchMessage();
    msg.setMessage(MSG.GO_SCHEDULE);
    RemoteActorsUtils.getInstance().getBatchMonitor().tell(msg, ActorRef.noSender());
}

Well, I'm not sure this helps a lot. But I also have this onStop method in the Global.java file, which is apparently never called :

@Override
public void onStop(Application app) {
    super.onStop(app);
    RemoteActorsUtils.getInstance().getSystem().shutdown();
    if (!RemoteActorsUtils.getInstance().getSystem().isTerminated()) {
        RemoteActorsUtils.getInstance().getSystem().shutdown();
    }

}

Thanks for the insight.