It was working well with previous releases and now is failling:
Exception in thread "main" [ObjectDB 2.3.7_20] javax.persistence.EntityNotFoundException
Entity is not found: MergeTest#('Hello',0) (error 631)
at com.objectdb.jpa.EMImpl.merge(EMImpl.java:451)
at MergeTest.main(MergeTest.java:19)
Thanks.