@Test
   public void shouldCascadeWithGroupsWithAlreadyExistingFaculty()
   {
      Faculty f = new Faculty();
      f.setName("FH");

      this.entityManager.persist(f);
      this.entityManager.flush();
      this.entityManager.clear();

      final Group g1 = new Group();
      g1.setName("Foobar");

      // associate both
      g1.setFaculty(f);
      f.getGroups().add(g1);

      this.entityManager.merge(f);

      Assert.assertNotNull(g1.getId());

      this.entityManager.flush();
      this.entityManager.clear();

      f = this.cut.readByPrimaryKey(f.getId());

      Assert.assertEquals("The two groups should be persited!", 1, f.getGroups().size());

   }

@Entity(name = "Groups")
@Table(uniqueConstraints = { @UniqueConstraint(columnNames = { "faculty_id", "name" }) })
public class Group implements Serializable
{
   @Id
   @GeneratedValue(strategy = GenerationType.AUTO)
   private Long         id;

   @ManyToOne(optional = false, cascade = { CascadeType.PERSIST, CascadeType.MERGE, CascadeType.DETACH })
   private Faculty         faculty;

   @Length(min = 1, max = 80)
   private String         name;

   @OneToMany(mappedBy = "group")
   private List<Timetable>   timetables   = new ArrayList<Timetable>();

   // Getter and Setter omitted
}

@Entity
public class Faculty implements Serializable
{
   @Id
   @GeneratedValue(strategy = GenerationType.AUTO)
   private Long      id;

   @Column(unique = true)
   @Length(min = 1, max = 80)
   private String      name;

   @OneToMany(mappedBy = "faculty", cascade = { CascadeType.PERSIST, CascadeType.MERGE, CascadeType.DETACH, CascadeType.REFRESH, CascadeType.REMOVE })
   private List<Group>   groups   = new ArrayList<Group>();

   // Getter and Setter omitted
}