With simple unit tests you do not use the process classloader from the database, but the normal classloader. Since the custom exception is on the latter it works. Afaik (but I'm not sure) jBPM only supports loading actionhandlers from the processclassloader and not all other classes. The 'solution' is to not put the Exception in the processarchive but on another (web/ear/system/...) classpath View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4249489#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...