使用实时数据，协程（Kotlin）测试视图模型

Posted 2023-01-20

几天来我一直在尝试测试我的视图模型，但没有成功。

这是我的视图模型：

class AdvertViewModel : ViewModel() 

    private val parentJob = Job()

    private val coroutineContext: CoroutineContext
        get() = parentJob + Dispatchers.Default

    private val scope = CoroutineScope(coroutineContext)

    private val repository : AdvertRepository = AdvertRepository(ApiFactory.Apifactory.advertService)

    val advertContactLiveData = MutableLiveData<String>()

    fun fetchRequestContact(requestContact: RequestContact) 
        scope.launch 
            val advertContact = repository.requestContact(requestContact)
            advertContactLiveData.postValue(advertContact)
        
    

这是我的存储库：

class AdvertRepository (private val api : AdvertService) : BaseRepository() 

    suspend fun requestContact(requestContact: RequestContact) : String? 

        val advertResponse = safeApiCall(
            call = api.requestContact(requestContact).await(),
            errorMessage = "Error Request Contact"
        )

        return advertResponse
    

这是我的视图模型测试：

@RunWith(JUnit4::class)
class AdvertViewModelTest 
    private val goodContact = RequestContact(...)

    private lateinit var advertViewModel: AdvertViewModel

    private var observer: Observer<String> = mock()

    @get:Rule
    var instantTaskExecutorRule = InstantTaskExecutorRule()

    @Before
    fun setUp() 
        advertViewModel = AdvertViewModel()
        advertViewModel.advertContactLiveData.observeForever(observer)
    

    @Test
    fun fetchRequestContact_goodResponse() 
        advertViewModel.fetchRequestContact(goodContact)

        val captor = ArgumentCaptor.forClass(String::class.java)

        captor.run 
            verify(observer, times(1)).onChanged(capture())
            assertEquals("someValue", value)
        
    

模拟方法（）：

inline fun <reified T> mock(): T = Mockito.mock(T::class.java)

我遇到此错误：

想要但不被调用：observer.onChanged（）;-> com.vizzit.AdvertViewModelTest.fetchRequestContact_goodResponse（AdvertViewModelTest.kt：52）实际上，与该模拟游戏的互动为零。

我不知道如何检索查询结果。

答案

您需要写一个OneTimeObserver来观察ViewModel中的实时数据>

class OneTimeObserver<T>(private val handler: (T) -> Unit) : Observer<T>, LifecycleOwner 
    private val lifecycle = LifecycleRegistry(this)

    init 
        lifecycle.handleLifecycleEvent(Lifecycle.Event.ON_RESUME)
    

    override fun getLifecycle(): Lifecycle = lifecycle

    override fun onChanged(t: T) 
        handler(t)
        lifecycle.handleLifecycleEvent(Lifecycle.Event.ON_DESTROY)
    

之后您可以编写扩展功能：

fun <T> LiveData<T>.observeOnce(onChangeHandler: (T) -> Unit) 
    val observer = OneTimeObserver(handler = onChangeHandler)
    observe(observer, observer)

比您可以检查我从项目中获得的this ViewModel class类，以在调用方法时（何时）检查ViewModel的情况。 

关于您的错误，它只是说LiveData方法从未被调用。