Matching Error (assertEquals) when unit testing ViewModel with Hilt and Mockk

Question

I am trying to unit test my ViewModel. My code is written using Kotlin, Android-X and Jetpack compose and I am using Hilt for Dependency Injection and Mockk for... Mocking

The issue I'm having is that when I run the test testMainMenuViewModel I receive the following error:

expected:<[image1.jpg, image2.jpg]> but was:<[]>
Expected :[image1.jpg, image2.jpg]
Actual   :[]

that relates to this line:

assertEquals(galleryList, viewModel.photoGalleryState.value)

photoGalleryState.value is assigned in the MainMenuViewModel, i.e. photoGalleryState.value = galleryRepository.getImageGalleryList()

and galleryRepository is mocked and 'every' call to getImageGalleryList is handled.

I'm not clear if I'm doing something wrong, i.e. the way I'm evaluating, or if I need to do something different because I am using Hilt.

I am using Hilt 2.46.1 (which doesn't support HilViewModelTest) and Mockk 1.13.5

In addition, if I add in the line verify { viewModel.photoGalleryState.value }

I receive the error

Missing calls inside verify { ... } block.
io.mockk.MockKException: Missing calls inside verify { ... } block.

My ViewModel class.

import androidx.compose.runtime.MutableState
import androidx.compose.runtime.mutableStateOf
import androidx.lifecycle.ViewModel
import com.xgame.xgarage.model.MenuItem
import com.xgame.xgarage.model.MenuItemRepository
import com.xgame.xgarage.model.MenuPhotoGalleryRepository
import dagger.hilt.android.lifecycle.HiltViewModel
import javax.inject.Inject

@HiltViewModel
class MainMenuViewModel @Inject constructor(
    galleryRepository: MenuPhotoGalleryRepository,
    menuItemRepository: MenuItemRepository
) : ViewModel() {
    val photoGalleryState: MutableState<List<String>> = mutableStateOf(emptyList())
    val itemMenuState: MutableState<List<MenuItem>> = mutableStateOf(emptyList())

    init {
        photoGalleryState.value = galleryRepository.getImageGalleryList()
        itemMenuState.value = menuItemRepository.getMenuItemsList()
    }
}

My ViewModel Unit Test

import com.xgames.xgarage.model.MenuItem
import com.xgames.xgarage.model.MenuItemRepository
import com.xgames.xgarage.model.MenuPhotoGalleryRepository
import io.mockk.MockKAnnotations
import io.mockk.every
import io.mockk.impl.annotations.RelaxedMockK
import org.junit.Assert.assertEquals
import org.junit.Before
import org.junit.Test

class MainMenuViewModelTest {

    @RelaxedMockK
    private lateinit var galleryRepository: MenuPhotoGalleryRepository

    @RelaxedMockK
    private lateinit var menuItemRepository: MenuItemRepository

    private lateinit var viewModel: MainMenuViewModel

    @Before
    fun setup() {
        MockKAnnotations.init(this)
        //galleryRepository = mockk<MenuPhotoGalleryRepository>()
        //menuItemRepository = mockk<MenuItemRepository>()
        viewModel = MainMenuViewModel(galleryRepository, menuItemRepository)
    }

    @Test
    fun testMainMenuViewModel() {
        // Prepare mock data
        val galleryList = listOf("image1.jpg", "image2.jpg")
        val menuList = listOf(MenuItem("file://some/file/name1.jpg", "1"), MenuItem("file://some/file/name2.jpg", "2"))

        // Mock repository methods
        every { galleryRepository.getImageGalleryList() } returns galleryList
        every { menuItemRepository.getMenuItemsList() } returns menuList

        // Verify the initial state of the view model
        //viewModel.photoGalleryState.value
        assertEquals(galleryList, viewModel.photoGalleryState.value)
        //assertEquals(menuList, viewModel.itemMenuState.value)
    }
}

MenuPhotoGalleryRepository

class MenuPhotoGalleryRepository {
    private val imageGalleryX = listOf(
        "file:///android_asset/images/cars/x1.jpg",
        "file:///android_asset/images/cars/x2.jpg",
        "file:///android_asset/images/cars/x3.jpg"
    )

    fun getImageGalleryList(): List<String> {
        return imageGalleryX
    }
}

MenuItem class

data class MenuItem(val imagePath: String, val menuName: String)

Usage of the ViewModel within my MainActivity class (used within a composable)

composable(route = "main_menu_screen") {
    val viewModel: MainMenuViewModel = hiltViewModel()
    MainMenuScreen(viewModel.photoGalleryState.value, viewModel.itemMenuState.value)
}

Any help or guidance is gratefully appreciated.

Answer 1

I think you need to change the test code like this

@Test
fun testMainMenuViewModel() {
    // Prepare mock data
    val galleryList = listOf("image1.jpg", "image2.jpg")
    val menuList = listOf(MenuItem("file://some/file/name1.jpg", "1"), MenuItem("file://some/file/name2.jpg", "2"))

    // Mock repository methods
    every { galleryRepository.getImageGalleryList() } returns galleryList
    every { menuItemRepository.getMenuItemsList() } returns menuList

    // create view model after defining actions of mock
    viewModel = MainMenuViewModel(galleryRepository, menuItemRepository)

    // Verify the initial state of the view model
    //viewModel.photoGalleryState.value
    assertEquals(galleryList, viewModel.photoGalleryState.value)
    //assertEquals(menuList, viewModel.itemMenuState.value)
}

When you create a view model in setup function, the init block of the view model will be invoked. So, the mocks are relaxed, they return empty list. I guess that what happened.