Hi -
There is a way to test the spam filtering in FOPE. To accomplish this, you must first upload the test users to FOPE. There are various ways to upload users to FOPE; the Add Users article (http://technet.microsoft.com/en-us/library/ff714987.aspx)
goes into more depth. Then you configure Directory-Based Edge Blocking to Pass Through, using the process described in the Configuring Directory-Based Edge Blocking article (http://technet.microsoft.com/en-us/library/ff715005.aspx).
This tells FOPE to filter mail for only the users you have uploaded to FOPE and to allow mail to recipients not on the list to simply pass through.
The one caveat here is that FOPE will perform edge blocking for ALL users, whether they are on the uploaded list or not. The pass through option will bypass the deeper spam checks that FOPE performs.
Micah