### Question:
RackDAO extends DefaultDAOBase<Integer, Rack> { public List<Rack> findRacks(final Datacenter datacenter) { return findRacks(datacenter, null); } RackDAO();  RackDAO(final EntityManager entityManager); List<Rack> findRacks(final Datacenter datacenter); List<Rack> findRacks(final Datacenter datacenter, final String filter); List<Rack> findRacksWithHAEnabled(final Datacenter datacenter); boolean existsAnyWithDatacenterAndName(final Datacenter datacenter, final String name); boolean existsAnyOtherWithDatacenterAndName(final Rack rack, final String name); List<Integer> getRackIdByMinVLANCount(final int idDatacenter); Long getNumberOfDeployedVlanNetworks(final Integer rackId); Rack findByIds(final Integer datacenterId, final Integer rackId); List<Rack> findAllNotManagedRacksByDatacenter(final Integer datacenterId); List<Rack> findAllNotManagedRacksByDatacenter(final Integer datacenterId,
        final String filter); @SuppressWarnings("unchecked") List<Integer> findUsedVrdpPorts(final Rack rack); Integer getEmptyOffMachines(final Integer rackId); Integer getEmptyOnMachines(final Integer rackId); List<Machine> getRandomMachinesToStartFromRack(final Integer rackId,
        final Integer howMany); List<Machine> getRandomMachinesToShutDownFromRack(final Integer rackId,
        final Integer howMany); List<Machine> getAllMachinesToShutDownFromRack(final Integer rackId);  }### Answer:
@Test public void test_findRacks() throws IllegalAccessException, InvocationTargetException, NoSuchMethodException { Datacenter datacenter1 = datacenterGenerator.createUniqueInstance(); Datacenter datacenter2 = datacenterGenerator.createUniqueInstance(); Rack rack2_1 = datacenter2.createRack("bRack_1", 2, 4094, 2, 10); Rack rack2_2 = datacenter2.createRack("aRack_2", 2, 4094, 2, 10); ds().persistAll(datacenter1, datacenter2, rack2_1, rack2_2); RackDAO dao = createDaoForRollbackTransaction(); Assert.assertEquals(dao.findRacks(reload(dao, datacenter1)).size(), 0); List<Rack> result = dao.findRacks(reload(dao, datacenter2)); assertEqualsPropertyForList(Rack.NAME_PROPERTY, result, "aRack_2", "bRack_1"); }