@Before
public void prepareDb() throws Exception {
getTransactionManager().begin();
final EntityManager em = getFactory().createEntityManager();
child11 = new Child();
child11.setName( "Emmanuel" );
em.persist( child11 );
child12 = new Child();
child12.setName( "Christophe" );
em.persist( child12 );
father1 = new Father();
father1.getOrderedChildren().add( child11 );
father1.getOrderedChildren().add( child12 );
em.persist( father1 );
child21 = new Child();
child21.setName( "Caroline" );
em.persist( child21 );
child22 = new Child();
child22.setName( "Thomas" );
em.persist( child22 );
father2 = new Father();
father2.getOrderedChildren().add( child21 );