Back to the actual problem: I also have this test case:
https://github.com/m-m-m/mmm/blob/master/mmm-persistence/mmm-persistence-impl-jpa/src/test/java/net/sf/mmm/persistence/impl/jpa/PersistenceTest.java

It is currently running. If I modify this entity used by the above test:
https://github.com/m-m-m/mmm/blob/master/mmm-persistence/mmm-persistence-impl-jpa/src/test/java/net/sf/mmm/persistence/impl/jpa/test/impl/DummyBarEntityImpl.java
from:
public class DummyBarEntityImpl extends AbstractJpaEntity<Long> implements DummyBarEntity {
to:
public class DummyBarEntityImpl extends JpaEntity implements DummyBarEntity {
the test fails with:
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'EntityManagerFactory' defined in class path resource [net/sf/mmm/persistence/beans-persistence-jpa-hibernate.xml]: Invocation of init method failed; nested exception is
...
Caused by: org.hibernate.MappingException: property mapping has wrong number of columns: net.sf.mmm.persistence.impl.jpa.test.impl.DummyFooEntityImpl.bar type: net.sf.mmm.persistence.impl.jpa.test.impl.DummyBarEntityImpl
at org.hibernate.mapping.PersistentClass.validate(PersistentClass.java:484)
at org.hibernate.mapping.RootClass.validate(RootClass.java:270)
at org.hibernate.cfg.Configuration.validate(Configuration.java:1324)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1786)
at org.hibernate.ejb.EntityManagerFactoryImpl.<init>(EntityManagerFactoryImpl.java:96)
at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:914)
... 42 more

However JpaEntity is nothing but this:
@MappedSuperclass
public abstract class JpaEntity extends AbstractJpaEntity<Long> {

/** UID for serialization. */
private static final long serialVersionUID = 4280571250879388596L;

/**

• The constructor.
  */
  public JpaEntity() { super(); }

/**

• {@inheritDoc}
  */
  @Override
  @Id
  @GeneratedValue(strategy = GenerationType.SEQUENCE)
  public Long getId() { return super.getId(); }
  
  /**
  * {@inheritDoc}

  */
  @Override
  public void setId(Long id)

  { super.setId(id); }

}