Examples of tests for: 1) testing MVP architecture (Model-View-Presenter Communication.kt) - tests communication between view and presenter and mocking repository behavior; 2) Repository (Repository.kt) - tests how data from local data source and remote data source is received and processed; 3) UI (UI (Integration).kt) - tests UI behavior

Model-View-Presenter Communication.kt

//imports are missing
class CardsListPresenterTest {
    private lateinit var presenter: CardsListPresenter
    private val view = mock<CardsListContact.View>()
    private val repository = mock<Repository>()
    private val scheduleProvider = ImmediateSchedulerProvider()
    
    // ... some other tests
    
    @Test
    fun createPresenter_setsPresenterToView() {
        presenter = CardsListPresenter(repository, view, scheduleProvider)

        verify(view).setPresenter(presenter)
    }

    @Test
    fun addCard_showAddCard() {
        presenter = CardsListPresenter(repository, view, scheduleProvider)

        presenter.addCard()
        verify(view).showAddCard()
    }
    
    @Test
    fun subscribe_showCardsIfCardsNotEmpty() {
        presenter = CardsListPresenter(repository, view, scheduleProvider)

        val notEmptyCreditCards = listOf(CreditCard())
        `when`(repository.getCreditCards()).thenReturn(Single.just(ResultWithPossibleException(notEmptyCreditCards.toOptional())))

        presenter.subscribe()
        verify(view).showCards(notEmptyCreditCards)
        assertEquals(true, presenter.currentCards == notEmptyCreditCards)
    }

    @Test
    fun subscribe_showNoCardsIfCardsEmpty() {
        presenter = CardsListPresenter(repository, view, scheduleProvider)

        val emptyCreditCards = listOf<CreditCard>()
        `when`(repository.getCreditCards()).thenReturn(Single.just(ResultWithPossibleException(emptyCreditCards.toOptional())))

        presenter.subscribe()
        verify(view).showNoCards()
        assertEquals(true, presenter.currentCards.isEmpty())
    }

    
    @Test
    fun deleteCard_showCardDeletedSuccessfully() {
        presenter = CardsListPresenter(repository, view, scheduleProvider)
        val someUUID = "someUUID"
        val someCompanyIdentifier = "someCompanyIdentifier"
        `when`(repository.deleteCreditCards(any()))
                .thenReturn(Completable.complete())
        presenter.deleteCreditCard(someUUID, someCompanyIdentifier)
        verify(view).showCardDeletedSuccessfully(someUUID, someCompanyIdentifier)
    }

    @Test
    fun deleteCard_showCardFailedToDelete() {
        presenter = CardsListPresenter(repository, view, scheduleProvider)
        val someUUID = "someUUID"
        val someCompanyIdentifier = "someCompanyIdentifier"
        `when`(repository.deleteCreditCards(any()))
                .thenReturn(Completable.error(Exception()))
        presenter.deleteCreditCard(someUUID, someCompanyIdentifier)
        verify(view).showCardFailedToDelete()

    }
    
    // ... some other tests
}

Repository.kt

//imports are missing
class RepositoryTest {

    private lateinit var mRepository: Repository

    private val mRemoteRepository = mock<DataSource>()
    private val mLocalRepository = mock<DataSource>()

    // ... some other tests

    @Before
    fun setupRepository() {
        mRepository = Repository.getInstance(mRemoteRepository, mLocalRepository)
    }

    @After
    fun destroyRepositoryInstance() {
        Repository.destroyInstance()
    }
    
    @Test
    fun authorize_SaveToCacheIfSuccess() {
        val credentials = Credentials(null, null, null)
        val someToken = "sometoken"
        `when`(mRemoteRepository.authorize(credentials)).thenReturn(Flowable.just(someToken))

        val testSubscriber = TestSubscriber<String>()
        mRepository.authorize(credentials).subscribe(testSubscriber)

        verify(mRemoteRepository).authorize(eq(credentials))
        verify(mLocalRepository).saveToken(eq(someToken))
    }


    @Test
    fun getConversationId_conversationIdIsRetrievedBothFromRemoteAndLocal() {
        val localConvId = ""
        val remoteConvId = ""
        setConversationIdAvailable(mLocalRepository, localConvId)
        setConversationIdAvailable(mRemoteRepository, remoteConvId)

        mRepository.getConversationId()

        verify(mLocalRepository).getConversationId()
        verify(mRemoteRepository).getConversationId()
    }

    @Test
    fun getConversationId_conversationIdRetrievedFromLocal_whenConvIdAvailableInLocalStorageAndRemoteStorageError() {
        val localConvId = "local"
        setConversationIdAvailable(mLocalRepository, localConvId)

        setConversationIdNotAvailableError(mRemoteRepository)
        val testSubscriberRemoteError = TestSubscriber<Optional<String>>()
        mRepository.getConversationId().subscribe(testSubscriberRemoteError)

        verify(mRemoteRepository).getConversationId()
        verify(mLocalRepository).getConversationId()
        testSubscriberRemoteError.assertValue(localConvId.toOptional())
    }

    // ... some other tests
}

UI (Integration).kt

//imports are missing
class CardsListScreenTest {
    @Rule
    @JvmField
    var mIntentTestRule: IntentsTestRule<CardsListActivity> =
            IntentsTestRule(CardsListActivity::class.java,
                    false,
                    false
            )

   // ... some other tests

    @Before
    fun startActivity() {
        val startIntent = Intent()
        mIntentTestRule.launchActivity(startIntent)
    }

    @After
    fun tearDown() {
        unregisterAllIdlingRegisterResources()
    }

    @Test
    fun testThatThatAddEditCardActivityOpenedAfterPressingAdd() {
        onView(withId(R.id.ic_add)).perform(ViewActions.click())
        Intents.intended(IntentMatchers.hasComponent(AddEditCardActivity::class.java.name))
    }

    @Test
    fun testThatThatEmptyScreenAndNotListIsShownByDefault() {
        onView(withId(R.id.cards_list)).check(matches(not(isDisplayed())))
        onView(withId(R.id.empty_view)).check(matches(isDisplayed()))
    }
    
    // ... some other tests
}