unit-testing - 协程测试异常不会被 TestCoroutineDispatcher 和 TestCoroutineScope 处理

Question

使用此 manual测试协程。编写一个预期会抛出异常的测试会崩溃而不是通过测试。我想知道我做错了什么。

    private val testDispatcher = TestCoroutineDispatcher()

    @Before
    fun setup() {
        // provide the scope explicitly, in this example using a constructor parameter
        Dispatchers.setMain(testDispatcher)
    }

    @After
    fun cleanUp() {
        Dispatchers.resetMain()
        testDispatcher.cleanupTestCoroutines()
    }

    @Test(expected = RuntimeException::class)
    fun testSomeFunctionWithException() = testDispatcher.runBlockingTest {
        someFunctionWithException()
    }


    private fun someFunctionWithException() {
        MainScope().launch {
            throw RuntimeException("Failed via TEST exception")
        }
    }

上面和下面的测试方法

    private val testScope = TestCoroutineScope()
    private lateinit var subject: Subject

    @Before
    fun setup() {
        // provide the scope explicitly, in this example using a constructor parameter
        subject = Subject(testScope)
    }

    @After
    fun cleanUp() {
        testScope.cleanupTestCoroutines()
    }


    @Test(expected = RuntimeException::class)
    fun testFooWithException() = testScope.runBlockingTest {
        subject.fooWithException()
    }

    class Subject(private val scope: CoroutineScope) {


        fun fooWithException() {
            scope.launch {
                println("fooWithException() thread: ${Thread.currentThread().name}")
                throw RuntimeException("Failed via TEST exception")
            }
        }
    }

即使他们都崩溃了

Note: Prefer to provide TestCoroutineScope when it does not complicate code since it will also elevate exceptions to test failures.

为什么两个都崩溃？

为什么具有范围的那个不会失败而不是崩溃？

Answer 1

TestCoroutineScope用途 TestCoroutineExceptionHandler它将处理协程中抛出的所有异常，将它们收集到 uncaughtExceptions 中。列表，尽管第一个将在 cleanUp 期间被重新抛出或更具体地说，当 cleanupTestCoroutines()被调用，因此您必须对该异常执行一些操作以防止测试失败。

@After
fun cleanUp() {
    try {
        testScope.cleanupTestCoroutines()
    } catch (e: Exception) {
        //Do something here
    }
}

在测试期间，您可以检查 uncaughtExceptions列出你的断言:

@Test(expected = RuntimeException::class)
fun testFooWithException() = testScope.runBlockingTest {
    subject.fooWithException()
    assertEquals(1, uncaughtExceptions.size)
    assertEquals(uncaughtExceptions[0].message, "Failed via TEST exception")
}