[rules-users] Extend Guvnor

Hi all, Long time user of Drools (dated back in xml syntax days). We are looking to revamp our in house rules product which is based on Drools 3.x. We have built a Swing thick client that provides similar functionality as Guvnor such as rule editing, versioning, deployment (with approval system). One major feature we do have is rule simulation. We allow user to simulate rules and display results while user save or seek approval of their rules before deploy to production system. The simulation feature allows user to run against production or testing environment to ensure it provide correct results. I wonder if Guvnor has such extensibility interface build in which I could add my own functionality such as simulation and result browsing? Since Guvnor is based on Seam and GWT (i think), I could probably fork the source and tweak the UI, but I much rather code against an interface supported by Drools. Thoughts? TIA. PS: I am curious how are existing Drools user test their rules currently? Andy