I have the same coEvery working without issue on PagingDataSource unit test but got exception while trying to write test against viewModel :

class PostViewModelTest {

    private val getPostUseCase : GetPostUseCase = mockk()
    private val viewModel = PostViewModel(getPostUseCase)

    @OptIn(ExperimentalCoroutinesApi::class)
    @Before
    fun setup() {
        Dispatchers.setMain(Dispatchers.Unconfined)
    }

    @OptIn(ExperimentalCoroutinesApi::class)
    @After
    fun tearDown() {
        Dispatchers.resetMain()
    }

    @Test
    fun test_items_contain_one_to_ten() = runTest {
        // Get the Flow of PagingData from the ViewModel under test


        // Given
        val expectedPostsList = List(23) {
            DomainModelFactory.getDefaultPostModel(UUID.randomUUID().toString())
        }

        coEvery { getPostUseCase.invoke(0) } returns ResultOf.Success(expectedPostsList)

        mockkStatic(Log::class)
        every { Log.isLoggable(any(), any()) } returns true
        every { Log.d(any(), any()) } returns 0

        val items: Flow<PagingData<PostModel>> = viewModel.uiState


        val itemsSnapshot: List<PostModel> = items.asSnapshot {
            // Scroll to the 50th item in the list. This will also suspend till
            // the prefetch requirement is met if there's one.
            // It also suspends until all loading is complete.
            scrollTo(index = 50)
        }

        // With the asSnapshot complete, you can now verify that the snapshot
        // has the expected values
        assertEquals(
            (0..50).map(Int::toString),
            itemsSnapshot
        )
    }
}