Coroutines-单元测试ViewModelScope.Launch方法

Question

测试失败，因为结果为空。为什么runblocking{...}不以阻塞的方式在ViewModel中运行launch块？

我知道，如果将其转换为返回deferred对象的async方法，则可以通过调用await()获取对象，或者可以返回job并调用join()。但是，我想通过将我的ViewModel方法保留为void函数来实现这一点，有没有办法做到这一点呢？

// MyViewModel.kt

class MyViewModel(application: Application) : AndroidViewModel(application) {

    val logic = Logic()
    val myLiveData = MutableLiveData<Result>()

    fun doSomething() {
        viewModelScope.launch(MyDispatchers.Background) {
            System.out.println("Calling work")
            val result = logic.doWork()
            System.out.println("Got result")
            myLiveData.postValue(result)
            System.out.println("Posted result")
        }
    }

    private class Logic {
        suspend fun doWork(): Result? {
          return suspendCoroutine { cont ->
              Network.getResultAsync(object : Callback<Result> {
                      override fun onSuccess(result: Result) {
                          cont.resume(result)
                      }

                     override fun onError(error: Throwable) {
                          cont.resumeWithException(error)
                      }
                  })
          }
    }
}

// MyViewModelTest.kt

@RunWith(RobolectricTestRunner::class)
class MyViewModelTest {

    lateinit var viewModel: MyViewModel

    @get:Rule
    val rule: TestRule = InstantTaskExecutorRule()

    @Before
    fun init() {
        viewModel = MyViewModel(ApplicationProvider.getApplicationContext())
    }

    @Test
    fun testSomething() {
        runBlocking {
            System.out.println("Called doSomething")
            viewModel.doSomething()
        }
        System.out.println("Getting result value")
        val result = viewModel.myLiveData.value
        System.out.println("Result value : $result")
        assertNotNull(result) // Fails here
    }
}

Answer 1

您需要做的是用给定的Dispatcher将coroutine的启动打包到一个块中。

var ui: CoroutineDispatcher = Dispatchers.Main
var io: CoroutineDispatcher =  Dispatchers.IO
var background: CoroutineDispatcher = Dispatchers.Default

fun ViewModel.uiJob(block: suspend CoroutineScope.() -> Unit): Job {
    return viewModelScope.launch(ui) {
        block()
    }
}

fun ViewModel.ioJob(block: suspend CoroutineScope.() -> Unit): Job {
    return viewModelScope.launch(io) {
        block()
    }
}

fun ViewModel.backgroundJob(block: suspend CoroutineScope.() -> Unit): Job {
    return viewModelScope.launch(background) {
        block()
    }
}

注意顶部的ui、io和背景。这里的一切都是顶级+扩展功能。

然后，在viewModel中，您可以像这样开始您的coroutine：

uiJob {
    when (val result = fetchRubyContributorsUseCase.execute()) {
    // ... handle result of suspend fun execute() here         
}

@ExperimentalCoroutinesApi
private fun unconfinifyTestScope() {
    ui = Dispatchers.Unconfined
    io = Dispatchers.Unconfined
    background = Dispatchers.Unconfined
}