It depends what is in your TestCoroutineRule class, but one thing you should definitely do is inject a TestDispatcher into your presenter, in place of both Dispatchers.Main and Dispatchers.IO.

I know this has been asked a number of different ways with a number of different answers but none I can see help my situation. I am trying to test a presenter using coroutines. In order to verify behaviour I have implemented com.nhaarman.mockitokotlin2.mock. All tests pass individually but when run together they fail randomly (2 pass, 1 pass, 3 pass etc.)

I don’t have that much experience with coroutines so I’m hoping someone with a bit more experience could steer me here. Below is my test class. I can add more info if required

package com.project.ui.search.results

import com.nhaarman.mockitokotlin2.mock
import com.nhaarman.mockitokotlin2.never
import com.nhaarman.mockitokotlin2.whenever
import ie.distilledsch.dschapi.models.search.SavedSearchCreateResponse
import io.reactivex.schedulers.TestScheduler
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.ExperimentalCoroutinesApi
import kotlinx.coroutines.runBlocking
import org.junit.Before
import org.junit.Rule
import org.junit.Test
import org.mockito.ArgumentMatchers
import org.mockito.Mock
import org.mockito.Mockito.doThrow
import org.mockito.Mockito.verify
import org.mockito.MockitoAnnotations
import retrofit2.HttpException

@ExperimentalCoroutinesApi
class SPSearchResultsPresenterSavedSearchesTest {

    @get:Rule val testCoroutineRule = TestCoroutineRule()
    private lateinit var interactor: SPSearchResultsInteractor
    @Mock private lateinit var view: SPSearchResultsView
    @Mock private lateinit var context: Context
    @Mock private lateinit var interactorBtwAdListAndAdDetails: InteractorBetweenListOfAdsAndAdDetails
    @Mock private lateinit var daftLoginManager: DaftLoginManager
    private lateinit var searchForm: SearchForm
    private lateinit var searchManager: SearchManager
    private lateinit var testScheduler: TestScheduler
    lateinit var presenter: SPSearchResultsPresenter

    @Before
    fun setup() {
        MockitoAnnotations.initMocks(this)
        interactor = mock()
        testScheduler = TestScheduler()
        searchForm = SearchForm()
        searchManager = SearchManager(searchForm)
        val presenterToTest = SPSearchResultsPresenterImpl(testScheduler, testScheduler,
                testScheduler, Dispatchers.Main, Dispatchers.IO, interactorBtwAdListAndAdDetails, daftLoginManager, context, view)
        presenterToTest.interactor = interactor
        presenterToTest.searchManager = searchManager
        presenter = presenterToTest
    }

    @Test
    fun `save search dialog confirm click success`() = runBlocking {
        val savedSearchTitle = "title"
        val savedSearchID = 1234
        val responseModel = SavedSearchCreateResponse(201, "Created", savedSearchID)
        whenever(interactor.saveNewSearch(savedSearchTitle)).thenReturn(responseModel)

        presenter.onSaveSearchDialogOkClick(savedSearchTitle)
        verify(interactor).saveNewSearch(savedSearchTitle)
        verify(view).displayIconForSavedSearch()
    }

    @Test
    fun `save search dialog confirm click failure`() = runBlocking {
        val savedSearchTitle = "title"
        val exception :HttpException = mock()

        doThrow(exception).`when`(interactor).saveNewSearch(savedSearchTitle)
        presenter.onSaveSearchDialogOkClick(savedSearchTitle)
        verify(interactor).saveNewSearch(savedSearchTitle)
        verify(view, never()).displayIconForSavedSearch()
        verify(view).showFetchSavedSearchFailedToast()
    }

    @Test
    fun `delete search success logged in`() = runBlocking {
        val savedSearchID = 1234
        whenever(interactor.isUserLoggedIn()).thenReturn(true)
        searchManager.isSearchSaved = true
        searchManager.savedSearchId = savedSearchID
        presenter.onSaveMenuItemClick()
        verify(interactor).deleteSavedSearch(savedSearchID)
        verify(view).displayIconForUnsavedSearch()
    }

    @Test
    fun `delete search error logged in`() = runBlocking {
        val savedSearchID = 1234
        val exception :HttpException = mock()
        whenever(interactor.isUserLoggedIn()).thenReturn(true)
        searchManager.isSearchSaved = true
        searchManager.savedSearchId = savedSearchID
        whenever(interactor.deleteSavedSearch(savedSearchID)).thenThrow(exception)
        presenter.onSaveMenuItemClick()
        verify(interactor).deleteSavedSearch(savedSearchID)
        verify(view, never()).displayIconForUnsavedSearch()
        verify(view).showSnackBar(ArgumentMatchers.anyInt())
    }

    @Test
    fun `click on save search not logged in` () = runBlocking {
        whenever(interactor.isUserLoggedIn()).thenReturn(false)
        presenter.onSaveMenuItemClick()
        verify(view).showLoginScreen()
    }
}