具有自己的协程范围的单元测试类

Question

我有一个看起来像这样的类

class Foo {
  private val scope = Job() + Dispatchers.IO
  val emissions = PublishSubject.create<Bar>()

  fun doSomething() {
    scope.launch {
      // Do a whole bunch of work...
      withContext(Dispatchers.Main) emissions.onNext(bar)
    }
  }
}

我正在尝试想出一种方法来对其进行单元测试。我已经尝试使范围可注入并编写类似

@Test fun testFoo() = runBlockingTest {
  Dispatchers.setMain(TestCoroutineDispatcher())
  val foo = Foo(this)
  foo.doSomething()
  foo.emissions.assertStuff()
}

但这似乎不起作用。断言发生在doSomething() 内部的协程完成之前。

我也尝试过使这个调度程序可注入，提供Dispatchers.Unconfined，但这也无济于事。这种方法有问题吗？

Answer 1

如果您能够将作业公开给公共 API，您可以尝试

class Foo {
  private val scope: CoroutineScope = CoroutineScope(Job() + Dispatchers.IO)
  val emissions = PublishSubject.create<Bar>()

  fun doSomething() = scope.launch {
    // Do a whole bunch of work...
    withContext(Dispatchers.Main) { emissions.onNext(bar) }
  }
}

class Test {
  private val testFoo = Foo()
  private val testObserver: TestObserver<Bar> = TestObserver.create()

  @BeforeEach
  fun setUp() {
    testFoo.emissions.subscribe(testObserver)
  }

  @Test fun testFoo() {
    runBlockingTest {
      Dispatchers.setMain(TestCoroutineDispatcher())
      testFoo.doSomething().join()
      testObserver.assertValue(bar)
    }
  }
}

Answer 2

用这个库可以很好地测试异步代码：Awaitility (or its kotlin extension)

你会这样写：

@Test fun testFoo() {

  val foo = Foo()

  foo.doSomething()

  await().atMost(5, MILLIS).until(/* your check like - foo.emissions.onNext(bar) */);
}