### Question:
MessengerServiceImpl implements MessengerService { @Override public List<Messenger> getAll() { return em.createQuery("FROM Messenger", Messenger.class).getResultList(); }  @Override List<Messenger> getAll(); @Override void addMessenger(Messenger messenger); @Override List<Messenger> getMessenger(String sendId, String receiveId); @Override int seenMessage(Messenger messenger); @Override List<Object> getInfo(String userId);  }### Answer:
@Test void allMessengerTest() { int size = initDataStore(); assertEquals(size, Messengerserviceimpl.getAll().size()); }