### Question:
PersistenceDelegator { public void refresh(Object entity) { if (contains(entity)) { MainCache mainCache = (MainCache) getPersistenceCache().getMainCache(); Node node = mainCache.getNodeFromCache(entity, getMetadata(entity.getClass()), this); try { lock.readLock().lock(); node.setPersistenceDelegator(this); node.refresh(); } finally { lock.readLock().unlock(); } } else { throw new IllegalArgumentException("This is not a valid or managed entity, can't be refreshed"); } } PersistenceDelegator(final KunderaMetadata kunderaMetadata, final PersistenceCache pc); void persist(Object e); E findById(final Class<E> entityClass, final Object primaryKey); List<E> find(Class<E> entityClass, Object... primaryKeys); List<E> find(Class<E> entityClass, Map<String, String> embeddedColumnMap); void remove(Object e); E merge(E e); void detach(Object entity); Client getClient(EntityMetadata m); Client getClient(final String persistenceUnit); EntityEventDispatcher getEventDispatcher(); boolean isOpen(); void refresh(Object entity); boolean isTransactionInProgress(); PersistenceCache getPersistenceCache(); KunderaMetadata getKunderaMetadata();  }### Answer:
@Test public void testRefresh() { PersonnelDTO dto = new PersonnelDTO(); dto.setPersonId("123"); PersistenceDelegator pd = ((EntityManagerImpl) em).getPersistenceDelegator(); try { pd.refresh(dto); } catch (IllegalArgumentException e) { Assert.assertEquals("This is not a valid or managed entity, can't be refreshed", e.getMessage()); } em.persist(dto); pd = ((EntityManagerImpl) em).getPersistenceDelegator(); try { em.refresh(dto); } catch (NullPointerException e) { Assert.assertTrue(true); } em.clear(); pd = ((EntityManagerImpl) em).getPersistenceDelegator(); try { pd.refresh(dto); } catch (IllegalArgumentException e) { Assert.assertEquals("This is not a valid or managed entity, can't be refreshed", e.getMessage()); } }