模擬時單元測驗協程空指標例外-有解無憂

我正在對以下課程進行單元測驗

class LoadTrendingSearchUseCaseImp @Inject constructor(
    private val searchCriteriaProvider: SearchCriteriaProvider,
    private val coroutineDispatcherProvider: CoroutineDispatcherProvider
) : LoadTrendingSearchUseCase {

    override suspend fun execute(): List<String> {
        return withContext(coroutineDispatcherProvider.io()) {
            searchCriteriaProvider.provideTrendingSearch().trendingSearches
        }
    }
}

interface SearchCriteriaProvider {
    suspend fun provideTrendingSearch(): CatalogSearchPage
}

class SearchCriteriaProviderImp() : SearchCritieraProvider {
    override suspend fun provideTrendingSearch(): CatalogSearchPage {
        return withContext(coroutineDispatcherProvider.io()) {
           /* long running task */
        }
    }
}

interface CoroutineDispatcherProvider {
    fun io(): CoroutineDispatcher = Dispatchers.IO

    fun default(): CoroutineDispatcher = Dispatchers.Default

    fun main(): CoroutineDispatcher = Dispatchers.Main

    fun immediate(): CoroutineDispatcher = Dispatchers.Main.immediate

    fun unconfined(): CoroutineDispatcher = Dispatchers.Unconfined
}

class CoroutineDispatcherProviderImp @Inject constructor() : CoroutineDispatcherProvider

這是我的實際測驗：

class LoadTrendingSearchUseCaseImpTest {
    private val searchCriteriaProvider: SearchCriteriaProvider = mock()
    private val coroutineDispatcherProvider = CoroutineDispatcherProviderImp()
    private lateinit var loadTrendingSearchUseCaseImp: LoadTrendingSearchUseCaseImp

    @Before
    fun setUp() {
        loadTrendingSearchUseCaseImp = LoadTrendingSearchUseCaseImp(
            searchCriteriaProvider,
            coroutineDispatcherProvider
        )
    }

    @Test
    fun `should provide trending searches`() {
        runBlockingTest {
            // Arrange
            // EXCEPTION HERE                whenever(searchCriteriaProvider.provideTrendingSearch().trendingSearches).thenReturn(
                emptyList()
            )

            // Act
            val actualResult = loadTrendingSearchUseCaseImp.execute()

            // Assert
            assertThat(actualResult).isEmpty()
        }
    }
}

實際的錯誤資訊：

  java.lang.NullPointerException
    .product_search.usecase.imp.LoadTrendingSearchUseCaseImpTest$should provide trending searches$1.invokeSuspend(LoadTrendingSearchUseCaseImpTest.kt:30)

uj5u.com熱心網友回復：

您試圖在存根方法時鏈接呼叫。

whenever(searchCriteriaProvider.provideTrendingSearch().trendingSearches)
  .thenReturn(emptyList())

在存根期間，實際的方法被呼叫。

searchCriteriaProvider.provideTrendingSearch()回傳 null，因為此呼叫尚未存根
后續呼叫null.trendingSearches導致 NPE

您需要存根鏈中的每個呼叫

whenever(searchCriteriaProvider.provideTrendingSearch())
  .thenReturn(catalogSearchPage)
whenever(catalogSearchPage.trendingSearches)
  .thenReturn(emptyList())

顯然，這假設

catalogSearchPage也是一個mock
trendingSearches是一個屬性

或者，您可以為構造一個 POJO catalogSearchPage，并在第一個存根中回傳它。

轉載請註明出處，本文鏈接：https://www.uj5u.com/qukuanlian/440120.html

標籤：单元测试科特林模仿者 kotlin 协程

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