MusicDetailViewModelTest.kt

class MusicDetailViewModelTest {

    private lateinit var SUT: MusicDetailViewModel

    private val repository: MusicRepository = mockk()
    private val savedInstanceStateHandle: SavedStateHandle = SavedStateHandle()

    @Before
    fun setUp() {
        Dispatchers.setMain(Dispatchers.Unconfined)

        SUT = MusicDetailViewModel(
            repository = repository, savedStateHandle = savedInstanceStateHandle
        )
    }

    @Test
    fun `given ViewModel initialise, then Empty state should be emitted`(): Unit = runBlocking {
        SUT = MusicDetailViewModel(
            repository = repository, savedStateHandle = savedInstanceStateHandle
        )

        SUT.state.test {
            val item = awaitItem()
            assertEquals(-1, item.uiMModel.trackId)
            assertEquals(true, item.uiMModel.musicTitle.isEmpty())
            assertEquals(true, item.uiMModel.artisName.isEmpty())
            assertEquals(true, item.uiMModel.albumName.isEmpty())
            assertEquals(true, item.uiMModel.previewUrl.isEmpty())
        }
    }

    @Test
    fun `give ViewModel initialize, when Music Id is passed, then Music Detail state should be emitted`(): Unit =
        runTest {
            coEvery { repository.getMusic(any()) } returns flowOf(musicEntity)

            SUT = MusicDetailViewModel(
                repository = repository,
                savedStateHandle = savedInstanceStateHandle
            )

            SUT.state.test {
                val firstItem = awaitItem()
                savedInstanceStateHandle[MUSIC_ID] = 121
                val secondState = awaitItem()
                assertEquals(musicEntity.trackId, secondState.uiMModel.trackId)
            }
        }

    @After
    fun tearDown() {
        Dispatchers.resetMain()
    }

    private val musicEntity = MusicEntity(
        trackId = 1441154571,
        artisName = "Rihanna",
        musicTitle = "Disturbia",
        albumName = "Good Girl Gone Bad: Reloaded",
        imageUrl = "https://is4-ssl.mzstatic.com/image/thumb/Music126/v4/2b/c0/81/2bc081c8-25f0-ba43-d451-587a54613778/16UMGIM59202.rgb.jpg/100x100bb.jpg",
        previewUrl = "https://audio-ssl.itunes.apple.com/itunes-assets/AudioPreview125/v4/a4/16/ce/a416ce10-e861-6e5a-194d-ad4fb2e4cd38/mzaf_7519322396128489319.plus.aac.p.m4a"
    )