android - 涉及 MutableSharedFlow 的测试 - java.lang.IllegalStateException : This job has not completed yet

Question

很抱歉这可能是一个非常业余的问题。我开始掌握流程，并在涉及 MutableSharedFlow 的测试中遇到问题。

以下是我可以构造的最简单的示例，它重现了该问题:

@ExperimentalCoroutinesApi
@ExperimentalTime
class MyExampleTest {

    val testDispatcher: TestCoroutineDispatcher = TestCoroutineDispatcher()

    @Test
    fun test() = testDispatcher.runBlockingTest  {
        val sharedFlow = MutableSharedFlow<String>()

        sharedFlow.take(2).collect {
            println(it)
        }

        sharedFlow.tryEmit("Hello")
        sharedFlow.tryEmit("World")
    }
}

这会导致以下错误:

java.lang.IllegalStateException: This job has not completed yet

    at kotlinx.coroutines.JobSupport.getCompletionExceptionOrNull(JobSupport.kt:1187)
    at kotlinx.coroutines.test.TestBuildersKt.runBlockingTest(TestBuilders.kt:53)
    at kotlinx.coroutines.test.TestBuildersKt.runBlockingTest(TestBuilders.kt:80)
    at com.example.MyExampleTest.test(MyExampleTest.kt:22)

根据我有限的理解，我认为这与 SharedFlow 从未完成这一事实有关。但我认为使用 take(2) 可以缓解这种情况。如有任何建议，我们将不胜感激!

Answer 1

From my limited understanding I think it's something to do with the fact that SharedFlow never completes.

你是对的，这或多或少就是问题所在。 Flow 基于协程，协程还没有完成。

在我看来，对 Flow 进行单元测试的最佳方法是 Turbine:

https://github.com/cashapp/turbine

// Cold Flow
flowOf("one", "two").test {
  assertEquals("one", expectItem())
  assertEquals("two", expectItem())
  expectComplete()
}

// Hot Flow
MutableStateFlow("test").test {
    assertThat(expectItem()).isEqualTo("test")
    cancelAndConsumeRemainingEvents()
}

关于这个确切的“问题”还有一个悬而未决的问题:

https://github.com/Kotlin/kotlinx.coroutines/issues/1204