Mockito does'nt mock repository

Question

i'm try to test my ViewModel with mockito.

This is my TestClass:

@RunWith(JUnit4::class)
class RatesViewModelTest {

    @Rule @JvmField
    open val instantExecutorRule = InstantTaskExecutorRule()

    @Mock
    var observer: Observer<Pair<ArrayList<CurrencyExchangerModel>,Boolean>>? = null

    @Mock
    private lateinit var repository: RatesRepository

    private var currencyList = ArrayList<CurrencyModel>()

    private lateinit var viewModel : RatesViewModel

    @Before
    fun setUp(){
        MockitoAnnotations.initMocks(this)

        currencyList.add(CurrencyModel("BASE"))
        viewModel = RatesViewModel(repository!!)
        viewModel.getCurrencyExchangerObservableList().observeForever(observer!!)
    }

    @Test
    fun testNull(){
        Mockito.`when`(repository.getFlowableRates()).thenReturn( Flowable.just(currencyList) )
        assertTrue(viewModel.getCurrencyExchangerObservableList().hasObservers())

    }
}

When this method is invoked:

Mockito.`when`(repository.getFlowableRates()).thenReturn( Flowable.just(currencyList) )

I got this error:

kotlin.UninitializedPropertyAccessException: lateinit property db has not been initialized

Here the repository:

open class RatesRepository(context:Context) : BaseRepository(context){

    @Inject
    lateinit var ratesAPI: RatesAPI

    @Inject
    lateinit var db: Database

    /**
     * load the updated chatList from API
     */
    fun loadCurrencyRatesFromAPI(): Single<ArrayList<CurrencyModel>> {
        val supportedCurrency = context.resources.getStringArray(R.array.currencies)
        return ratesAPI.getLatestRates(EUR_CURRENCY_ID).map { RatesConverter.getRatesListFromDTO(it,supportedCurrency) }
    }

    /**
     * save rates on DB
     */
    fun saveCurrencyRatesOnDB(list:ArrayList<CurrencyModel>): Completable {
        return db.currencyRatesDAO().insertAll(list)
    }

    /**
     * get flawable rates from DB
     */
    fun getFlowableRates(): Flowable<List<CurrencyModel>> {
        return db.currencyRatesDAO().getAll()
    }

    companion object {
        const val EUR_CURRENCY_ID = "EUR" //BASE
    }
}

What i'm doing wrong ?

Thx !

Answer 1

When you define behaviour of a mock and use the when(...).then(...) notation of mockito,
the method itself is invoked (by mockito, normally not relevant for your test).

In your case that is a problem because db is not initialized.

To avoid this issues use the doReturn(...).when(...) syntax in these cases,
which does not cause the method invocation.

Mockito.doReturn(Flowable.just(currencyList)).when(repository).getFlowableRates();

(You might need to adjust this java syntax to make it kotlin compatible)