JUnit test not sending values as parameters to function (Kotlin)

Question

I am creating a simple junit test to test a function in my view model but the first assertion fails as the function I call returns null. When I debug the function I call has null parameters which is weird cause I pass them in.

I have spent time debugging and searching for why I am having that issue but I have found nothing that fixes my issue or tells me what the issue is.

@RunWith(MockitoJUnitRunner::class)
class CurrencyUnitTest {

    @Rule
    @JvmField
    val rule = InstantTaskExecutorRule()

    @Mock
    val currencyViewModel : CurrencyViewModel = mock(CurrencyViewModel::class.java)

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

        val rates: HashMap<String, Double> =
                hashMapOf(
                    "USD" to 1.323234,
                    "GBP" to 2.392394,
                    "AUD" to 0.328429,
                    "KWR" to 893.4833
                )

        val currencyRates = MutableLiveData<Resource<CurrencyRatesData?>>()
        val resource = Resource<CurrencyRatesData?>(Status.SUCCESS, CurrencyRatesData("CAD", rates, 0))
        currencyRates.value = resource

        `when`(currencyViewModel.currencyRatesData).thenReturn(currencyRates)

        val baseCurrency = MutableLiveData<String>()
        baseCurrency.value = "CAD"

        `when`(currencyViewModel.baseCurrency).thenReturn(baseCurrency)
    }

    @Test
    fun calculateValueTest() {
        // this fails
        assertEquals("0.36", currencyViewModel.calculateValue("AUD", "1.11"))
    }
}

Answer 1

Mocked classes will not really be called. If you want to test your currencyViewModel.calculateValue() method, create a real object of that class and mock possible constructor arguments.