### Question:
ChatRepository { public void addMessage(ChatMessage message) { backgroundHandler.post(() -> { chatDao.save(message); }); } ChatRepository(ChatDao chatDao, RequestEncoder encoder,
                          Handler backgroundHandler); void addMessage(ChatMessage message); LiveData<PagedList<ChatMessage>> getMessagesByGroupId(int groupId); void requestSendMessage(int groupId, String message); void deleteAllMessages();  }### Answer:
@Test public void addMessageTest() { testChatRepository.addMessage(mockMessage); verify(mockChatDao).save(mockMessage); }