I'm not trying to convince you to drop GlassFish, but your testing environment need to take into consideration Java EE rules.
EntityManager is not published to the global JNDI, so its visibility is limited to the Java EE components and persistent unit scoping rules. E.g. you can look it up from an EJB (if this PU is scoped to be visible to this EJB) but not a simple Java SE client or a different application deployed to the same server.
Regards,
-marina
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