android - 单元测试新的 Kotlin 协程 StateFlow

Question

最近上课 StateFlow was introduced作为 Kotlin 协程的一部分。
我目前正在尝试它并在尝试对我的 ViewModel 进行单元测试时遇到问题。我想要实现的目标:测试我的 StateFlow 是否在我的 ViewModel 中以正确的顺序接收所有状态值。
我的代码如下。
View 模型:

class WalletViewModel(private val getUserWallets: GetUersWallets) : ViewModel() {

val userWallet: StateFlow<State<UserWallets>> get() = _userWallets
private val _userWallets: MutableStateFlow<State<UserWallets>> =
        MutableStateFlow(State.Init)

fun getUserWallets() {
    viewModelScope.launch {
        getUserWallets.getUserWallets()
            .onStart { _userWallets.value = State.Loading }
            .collect { _userWallets.value = it }
    }
}

我的测试:

@Test
fun `observe user wallets ok`() = runBlockingTest {
    Mockito.`when`(api.getAssetWallets()).thenReturn(TestUtils.getAssetsWalletResponseOk())
    Mockito.`when`(api.getFiatWallets()).thenReturn(TestUtils.getFiatWalletResponseOk())

    viewModel.getUserWallets()
        
    val res = arrayListOf<State<UserWallets>>()
    viewModel.userWallet.toList(res) //doesn't works

    Assertions.assertThat(viewModel.userWallet.value is State.Success).isTrue() //works, last value enmited
}

访问发出的最后一个值有效。但我要测试的是所有发出的值都以正确的顺序发出。
使用这段代码:viewModel.userWallet.toList(res)我收到以下错误:

java.lang.IllegalStateException: This job has not completed yet
    at kotlinx.coroutines.JobSupport.getCompletionExceptionOrNull(JobSupport.kt:1189)
    at kotlinx.coroutines.test.TestBuildersKt.runBlockingTest(TestBuilders.kt:53)
    at kotlinx.coroutines.test.TestBuildersKt.runBlockingTest$default(TestBuilders.kt:45)
    at WalletViewModelTest.observe user wallets ok(WalletViewModelTest.kt:52)
....

我想我错过了一些明显的东西。但不知道为什么当我刚刚开始使用协程和 Flow 时，这个错误似乎在不使用 runBlockingTest 时发生，我已经使用了。
编辑:
作为临时解决方案，我将其作为实时数据进行测试:

@Captor
lateinit var captor: ArgumentCaptor<State<UserWallets>>
    
@Mock
lateinit var walletsObserver: Observer<State<UserWallets>>

@Test
fun `observe user wallets ok`() = runBlockingTest {
    viewModel.userWallet.asLiveData().observeForever(walletsObserver)
    
    viewModel.getUserWallets()
    captor.run {
        Mockito.verify(walletsObserver, Mockito.times(3)).onChanged(capture())
        Assertions.assertThat(allValues[0] is State.Init).isTrue()
        Assertions.assertThat(allValues[1] is State.Loading).isTrue()
        Assertions.assertThat(allValues[2] is State.Success).isTrue()
    }
}

Answer 1

SharedFlow/StateFlow 是一个热流，如文档中所述，A shared flow is called hot because its active instance exists independently of the presence of collectors.这意味着，启动流程集合的范围不会自行完成。
要解决此问题，您需要取消调用 collect 的范围，并且由于您的测试范围是测试本身，因此无法取消测试，因此您需要在不同的作业中启动它。

@Test
fun `Testing a integer state flow`() = runBlockingTest{
    val _intSharedFlow = MutableStateFlow(0)
    val intSharedFlow = _intSharedFlow.asStateFlow()
    val testResults = mutableListOf<Int>()

    val job = launch {
        intSharedFlow.toList(testResults)
    }
    _intSharedFlow.value = 5

    assertEquals(2, testResults.size)
    assertEquals(0, testResults.first())
    assertEquals(5, testResults.last())
    job.cancel()
}

您的具体用例:

@Test
fun `observe user wallets ok`() = runBlockingTest {
    whenever(api.getAssetWallets()).thenReturn(TestUtils.getAssetsWalletResponseOk())
    whenever(api.getFiatWallets()).thenReturn(TestUtils.getFiatWalletResponseOk())

    viewModel.getUserWallets()

    val result = arrayListOf<State<UserWallets>>()
    val job = launch {
        viewModel.userWallet.toList(result) //now it should work
    }

    Assertions.assertThat(viewModel.userWallet.value is State.Success).isTrue() //works, last value enmited
    Assertions.assertThat(result.first() is State.Success) //also works
    job.cancel()
}

两个重要的事情:

始终取消您创建的工作以避免java.lang.IllegalStateException: This job has not completed yet

由于这是一个 StateFlow，当开始收集(在 toList 内)时，您会收到最后一个状态。但是如果你第一次开始收集，然后你调用你的函数 viewModel.getUserWallets() ，然后在 result 内列表，您将拥有所有状态，以防您也想对其进行测试。