Hello I am implementing one sample for unit testing This is

Question

Hello I am implementing one sample for unit testing This is my test class ``` SmallTest RunWith MockitoJUnitRunner class ExperimentalCoroutinesApi class CharacterViewModelTest get Rule val instantTaskExecutorRule = InstantTaskExecutorRule get Rule val testCoroutineRule = TestCoroutineRule Mock lateinit var characterUseCase CharacterUsecase Mock lateinit var characterRepository CharacterRepository Mock lateinit var characterLiveData Observer lt UiState lt ArrayList lt CharacterItem gt gt gt private val characterViewModel CharacterViewModel by lazy CharacterViewModel characterUseCase Test fun test characterApiCallSuccess stubCharacterApiSuccess characterViewModel charactersLiveEvent observeForever characterLiveData characterViewModel getCharacters 1 verify characterLiveData onChanged UiState Loading Test Loading Response verify characterLiveData onChanged UiState Success characterApiResponse Test Success Response characterViewModel charactersLiveEvent removeObserver characterLiveData private fun stubCharacterApiSuccess testCoroutineRule runBlockingTest doReturn characterApiResponse `when` characterRepository getCharacters 1 ``` I am getting below error `Wanted but not invoked ` `characterLiveData onChanged ` `Success data= CharacterItem name=Rick Sanchez image=<https rickandmortyapi com api character avatar 1 jpeg> status=Alive gender=Male species=Human ` ` ` ` gt at com example databindingsample CharacterViewModelTest test characterApiCallSuccess CharacterViewModelTest kt 55 ` `Actually there were zero interactions with this mock ` I can t figure out what this error is saying Is there any thing i am doing wrong Any one have any idea about it

Klaas Kabini · Answer

Your unit test is incorrect You have to verify the behaviour of the collaborator which is the CharacterUseCase not the observer The observer is not the collaborator The CharacterUseCase is the interactor or collaborator that is used by the view model to achieve a specific use case

Klaas Kabini · Answer

I also noticed that when observing using non lifecycle bound observers the onChanged does not get called at times and behaves strangely I had to do this to get it to catch the onChanged events ```fun lt T gt LiveData lt T gt attachDisposableObserver time Long = 2 timeUnit TimeUnit = TimeUnit SECONDS afterObserve gt Unit val latch = CountDownLatch 1 val observer = object Observer lt T gt override fun onChanged t T latch countDown this gattachDisposableObserver removeObserver this this observeForever observer try Don t wait indefinitely if the LiveData is not set if latch await time timeUnit throw TimeoutException LiveData value was never set finally this removeObserver observer afterObserve invoke ```