SomeViewModel.kt

class SomeViewModelTest {

    private lateinit var someViewModel: SomeViewModel
    private val someInteractor: SomeInteractor = mockk(relaxed = true)
    private val dataToLoad: String = "Data to load"

    @Before
    fun setUp() {
        clearAllMocks()
    }

    @Test
    fun `Loader should be shown when data is being loaded`() = runTest {
        coEvery { someInteractor.loadSomething() } coAnswers {
            delay(1_000)
            dataToLoad
        }
        val dispatechers = TestDispatchersProvider(testScheduler)

        someViewModel = SomeViewModel(someInteractor, dispatechers)
        runCurrent()

        // Replaced with veryfier
        assertThat(someViewModel)
            .loaderIsShown()
            .errorIsHidden()
            .contentIsHidden()
    }

    @Test
    fun `Should show content if data is loaded`() = runTest {
        coEvery { someInteractor.loadSomething() } returns dataToLoad
        val dispatechers = TestDispatchersProvider(testScheduler)

        someViewModel = SomeViewModel(someInteractor, dispatechers)
        runCurrent()

        // Replaced with veryfier
        assertThat(someViewModel)
            .contentIsShow(dataToLoad)
            .errorIsHidden()
            .loaderIsHidden()
    }

    @Test
    fun `Should show error state if error appeared`() = runTest {
        coEvery { someInteractor.loadSomething() } coAnswers { throw Throwable() }
        val dispatechers = TestDispatchersProvider(testScheduler)

        someViewModel = SomeViewModel(someInteractor, dispatechers)
        runCurrent()
        
        // Replaced with veryfier
        assertThat(someViewModel)
            .errorIsShown()
            .contentIsHidden()
            .loaderIsHidden()
    }
    
    @Test
    fun `Should show content state if user clicks on retry button after loading data with error`() = runTest {
        coEvery { someInteractor.loadSomething() } coAnswers { throw Throwable() }
        val dispatechers = TestDispatchersProvider(testScheduler)

        someViewModel = SomeViewModel(someInteractor, dispatechers)
        runCurrent()
        
        coEvery { someInteractor.loadSomething() } returns dataToLoad
        someViewModel.onRetryButtonClicked()
        
        // Replaced with veryfier
        assertThat(someViewModel)
            .contentIsShow(dataToLoad)
            .errorIsHidden()
            .loaderIsHidden()
    }
}