I would like to test case when server does not return response, and we trigger the next network call ( like for example search query).
So we basically have a method inside ViewModel and Retrofit method
interface RetrofitApi {
@GET("Some Url")
suspend fun getVeryImportantStuff(): String
}
class TestViewModel(private val api: RetrofitApi) : ViewModel() {
private var askJob: Job? = null
fun load(query: String) {
askJob?.cancel()
askJob = viewModelScope.launch {
val response = api.getVeryImportantStuff()
//DO SOMETHING WITH RESPONSE
}
}
}
And I would like to test case when new query is asked, and the old one didn't returns. for case when response returns test is easy
@Test
fun testReturnResponse() {
runBlockingTest {
//given
val mockApi:RetrofitApi = mock()
val viewModel = TestViewModel(mockApi)
val response = "response from api"
val query = "fancy query"
whenever(mockApi.getVeryImportantStuff()).thenReturn(response)
//when
viewModel.load(query)
//then
//verify what happens
}
}
But I don't know how to mock suspend function that did't come back, and test case when new request is triggered like this
@Test
fun test2Loads() {
runBlockingTest {
//given
val mockApi:RetrofitApi = mock()
val viewModel = TestViewModel(mockApi)
val response = "response from api"
val secondResponse = "response from api2"
val query = "fancy query"
whenever(mockApi.getVeryImportantStuff())
.thenReturn(/* Here return some fancy stuff that is suspend* or something like onBlocking{} stub but not blocking but dalayed forever/)
.thenReturn(secondResponse)
//when
viewModel.load(query)
viewModel.load(query)
//then
//verify that first response did not happens , and only second one triggered all the stuff
}
}
Any ideas ?
EDIT: I'm not really attached to mockito, any mock library will be good :) regards Wojtek
I came up with kind of solution to the problem, but slightly different than I was thinking at the beginning
interface CoroutineUtils {
val io: CoroutineContext
}
interface RetrofitApi {
@GET("Some Url")
suspend fun getVeryImportantStuff(query: String): String
}
class TestViewModel(private val api: RetrofitApi,
private val utils: CoroutineUtils) : ViewModel() {
private val text = MutableLiveData<String>()
val testStream: LiveData<String> = text
private var askJob: Job? = null
fun load(query: String) {
askJob?.cancel()
askJob = viewModelScope.launch {
val response = withContext(utils.io) { api.getVeryImportantStuff(query) }
text.postValue(response)
}
}
}
And the test scenario would look like this
class TestViewModelTest {
@get:Rule
val coroutineScope = MainCoroutineScopeRule()
@get:Rule
val instantTaskExecutorRule = InstantTaskExecutorRule()
lateinit var retrofit: RetrofitApi
lateinit var utils: CoroutineUtils
val tottalyDifferentDispatcher = TestCoroutineDispatcher()
lateinit var viewModel: TestViewModel
@Before
fun setup() {
retrofit = mock()
utils = mock()
viewModel = TestViewModel(retrofit, utils)
}
@UseExperimental(ExperimentalCoroutinesApi::class)
@Test
fun test2Loads() {
runBlockingTest {
//given
val response = "response from api"
val response2 = "response from api2"
val query = "fancy query"
val query2 = "fancy query2"
whenever(utils.io)
.thenReturn(tottalyDifferentDispatcher)
val mutableListOfStrings = mutableListOf<String>()
whenever(retrofit.getVeryImportantStuff(query)).thenReturn(response)
whenever(retrofit.getVeryImportantStuff(query2)).thenReturn(response2)
//when
viewModel.testStream.observeForever {
mutableListOfStrings.add(it)
}
tottalyDifferentDispatcher.pauseDispatcher()
viewModel.load(query)
viewModel.load(query2)
tottalyDifferentDispatcher.resumeDispatcher()
//then
mutableListOfStrings shouldHaveSize 1
mutableListOfStrings[0] shouldBe response2
verify(retrofit, times(1)).getVeryImportantStuff(query2)
}
}
}
It is not exactly what I wanted, because retrofit call is not triggered when load method is called for the first time, but it is the closest solution.
What would be a perfect test for me will be assertion that retrofit was called twice , but only the second one returned to ViewModel. Solution for that will be to wrap Retrofit around method that returns suspend function like this
interface RetrofitWrapper {
suspend fun getVeryImportantStuff(): suspend (String)->String
}
class TestViewModel(private val api: RetrofitWrapper,
private val utils: CoroutineUtils) : ViewModel() {
private val text = MutableLiveData<String>()
val testStream: LiveData<String> = text
private var askJob: Job? = null
fun load(query: String) {
askJob?.cancel()
askJob = viewModelScope.launch {
val veryImportantStuff = api.getVeryImportantStuff()
val response = withContext(utils.io) {
veryImportantStuff(query)
}
text.postValue(response)
}
}
}
and test for it
@Test
fun test2Loads() {
runBlockingTest {
//given
val response = "response from api"
val response2 = "response from api2"
val query = "fancy query"
val query2 = "fancy query2"
whenever(utils.io)
.thenReturn(tottalyDifferentDispatcher)
val mutableListOfStrings = mutableListOf<String>()
whenever(retrofit.getVeryImportantStuff())
.thenReturn(suspendCoroutine {
it.resume { response }
})
whenever(retrofit.getVeryImportantStuff()).thenReturn(suspendCoroutine {
it.resume { response2 }
})
//when
viewModel.testStream.observeForever {
mutableListOfStrings.add(it)
}
tottalyDifferentDispatcher.pauseDispatcher()
viewModel.load(query)
viewModel.load(query2)
tottalyDifferentDispatcher.resumeDispatcher()
//then
mutableListOfStrings shouldHaveSize 1
mutableListOfStrings[0] shouldBe response2
verify(retrofit, times(2)).getVeryImportantStuff()
}
}
But in my opinion it is a little bit too much in interference in code only to be testable. But maybe I'm wrong :P