got an javax.jdo.JDOFatalUserException ?

I was experimenting with junit test in combination with the JDO bundled with google app-engines java framwork when I got this message: "javax.jdo.JDOFatalUserException: No PersistenceManagerFactory configurable via properties resource "" or no named PMF or persistence unit named "" found."

This was resolved by replacing
pmf = JDOHelper.getPersistenceManagerFactory();
with
pmf = JDOHelper.getPersistenceManagerFactory("transactions-optional");

Duh.