android - 如何运行协程作为单元测试的阻塞？

Question

我已经开始为我的 MVP Android 项目编写单元测试，但是我依赖于协程的测试间歇性地失败(通过日志记录和调试，我确认验证有时会提前发生，添加 delay 可以解决这个问题当然)

我已经尝试使用 runBlocking 进行包装，并且我从 org.jetbrains.kotlinx:kotlinx-coroutines-test 中发现了 Dispatchers.setMain(mainThreadSurrogate) ，但是尝试了这么多组合至今都没有取得任何成功。

abstract class CoroutinePresenter : Presenter, CoroutineScope {
    private lateinit var job: Job

    override val coroutineContext: CoroutineContext
        get() = job + Dispatchers.Main

    override fun onCreate() {
        super.onCreate()
        job = Job()
    }

    override fun onDestroy() {
        super.onDestroy()
        job.cancel()
    }
}

class MainPresenter @Inject constructor(private val getInfoUsecase: GetInfoUsecase) : CoroutinePresenter() {
    lateinit var view: View

    fun inject(view: View) {
        this.view = view
    }

    override fun onResume() {
        super.onResume()

        refreshInfo()
    }

    fun refreshInfo() = launch {
        view.showLoading()
        view.showInfo(getInfoUsecase.getInfo())
        view.hideLoading()
    }

    interface View {
        fun showLoading()
        fun hideLoading()

        fun showInfo(info: Info)
    }
}

class MainPresenterTest {
    private val mainThreadSurrogate = newSingleThreadContext("Mocked UI thread")

    private lateinit var presenter: MainPresenter
    private lateinit var view: MainPresenter.View

    val expectedInfo = Info()

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

        view = mock()

        val mockInfoUseCase = mock<GetInfoUsecase> {
            on { runBlocking { getInfo() } } doReturn expectedInfo
        }

        presenter = MainPresenter(mockInfoUseCase)
        presenter.inject(view)
        presenter.onCreate()
    }

    @Test
    fun onResume_RefreshView() {
        presenter.onResume()

        verify(view).showLoading()
        verify(view).showInfo(expectedInfo)
        verify(view).hideLoading()
    }

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

我相信 runBlocking block 应该强制所有子 coroutineScopes 在同一个线程上运行，强制它们在继续验证之前完成。

Answer 1

在 CoroutinePresenter 类中，您正在使用 Dispatchers.Main。您应该能够在测试中更改它。尝试执行以下操作:

1. 将 uiContext: CoroutineContext 参数添加到演示者的构造函数中:

   abstract class CoroutinePresenter(private val uiContext: CoroutineContext = Dispatchers.Main) : CoroutineScope {
   private lateinit var job: Job
   
   override val coroutineContext: CoroutineContext
       get() = uiContext + job
   
   //...
   }
   
   class MainPresenter(private val getInfoUsecase: GetInfoUsecase, 
                       private val uiContext: CoroutineContext = Dispatchers.Main 
   ) : CoroutinePresenter(uiContext) { ... }
   

2. 更改 MainPresenterTest 类以注入(inject)另一个 CoroutineContext:

   class MainPresenterTest {
       private lateinit var presenter: MainPresenter
   
       @Mock
       private lateinit var view: MainPresenter.View
   
       @Mock
       private lateinit var mockInfoUseCase: GetInfoUsecase
   
       val expectedInfo = Info()
   
       @Before
       fun setUp() {
           // Mockito has a very convenient way to inject mocks by using the @Mock annotation. To
           // inject the mocks in the test the initMocks method needs to be called.
           MockitoAnnotations.initMocks(this)
   
           presenter = MainPresenter(mockInfoUseCase, Dispatchers.Unconfined) // here another CoroutineContext is injected 
           presenter.inject(view)
           presenter.onCreate()
   }
   
       @Test
       fun onResume_RefreshView() = runBlocking {
           Mockito.`when`(mockInfoUseCase.getInfo()).thenReturn(expectedInfo)
   
           presenter.onResume()
   
           verify(view).showLoading()
           verify(view).showInfo(expectedInfo)
           verify(view).hideLoading()
       }
   }