@BeforeAll
public void setUp(SessionFactoryScope scope) {
  scope.inTransaction(
      session -> {
        Agency agency = new Agency( 1, "Test Agency" );
        Group group = new Group( 1, "Test Group 1" );
        agency.addGroup(group);
        for ( int i = 1; i < 9; i++ ) {
          User user = new User( i, "User " + i );
          agency.addUser(user);
          group.addUser(user);
        }
        session.persist( agency );
      }
   );
 }

public void addGroup(Group group){
   if (groups == null){
      groups = new HashSet<>();
       }
   groups.add( group );
   group.setAgency( this );
}