@Test
 public void oidGeneratorStoredOnceSaved() throws Exception {
   persistedObjects.saveOidGeneratorMemento(mockMemento);
   final IdentifierGeneratorDefault.Memento oidGeneratorMemento =
       persistedObjects.getOidGeneratorMemento();
   assertThat(oidGeneratorMemento, is(mockMemento));
 }
 @Test
 public void noOidGeneratorInitially() throws Exception {
   final IdentifierGeneratorDefault.Memento oidGeneratorMemento =
       persistedObjects.getOidGeneratorMemento();
   assertThat(oidGeneratorMemento, is(nullValue()));
 }