java - Junit/Mockito - 等待方法执行

Question

在我的应用程序中，我对某些操作使用了观察者模式，我想在单元测试中测试它们。问题是我不知道如何使用 junit/mockito/其他东西测试观察者。有帮助吗？

例如这是我的单元测试:

@Before
public void setUp() throws IOException, Exception {
    observer = new GameInstanceObserver(); // observable (GameInstance) will call update() method after every change
    GameInstance.getInstance().addObserver(observer); // this is observable which is updated by serverService
}

@Test(expected = UserDataDoesntExistException.class)
public void getRoomUserData_usingNullKey_shouldThrowUserDataDoesntExist() throws InterruptedException, UserDataDoesntExistException {
    serverService.createRoom("exampleRoom"); // this operation is asynchronous and updates GameInstance data (as I wrote before GameInstance is Observable)
    Thread.sleep(400); // how to do it in better way?

    GameInstance gi = (GameInstance) observer.getObservable();
    assertTrue(gi.getRoom("exampleRoom").getRoomId().equals("exampleRoom"));
}

我不想使用 Thread.sleep() 并以那种方式(或类似方式)使用它:

@Test(expected = UserDataDoesntExistException.class)
public void getRoomUserData_usingNullKey_shouldThrowUserDataDoesntExist() throws InterruptedException, UserDataDoesntExistException {
    serverService.createRoom("exampleRoom"); // this operation is asynchronous and updates GameInstance data (as I wrote before GameInstance is Observable)
    waitUntilDataChange(GameInstance.getInstance()); // wait until observable will be changed so I know that it notified all observer and I can validate data

    GameInstance gi = (GameInstance) observer.getObservable();
    assertTrue(gi.getRoom("exampleRoom").getRoomId().equals("exampleRoom"));
}

Answer 1

如果我没理解错的话，问题其实不是测试观察者，而是测试一个异步方法调用的结果。为此，创建一个观察器，它会阻塞直到调用其 update() 方法。类似于以下内容:

public class BlockingGameObserver extends GameInstanceObserver {
    private CountDownLatch latch = new CountDownLatch(1);

    @Override
    public void update() {
        latch.countDown();
    }

    public void waitUntilUpdateIsCalled() throws InterruptedException {
        latch.await();
    }
}

在你的测试中:

private BlockingGameObserver observer;

@Before
public void setUp() throws IOException, Exception {
    observer = new BlockingGameObserver();
    GameInstance.getInstance().addObserver(observer); 
}

@Test
public void getRoomUserData_usingNullKey_shouldThrowUserDataDoesntExist() throws InterruptedException, UserDataDoesntExistException {
    serverService.createRoom("exampleRoom");   
    observer.waitUntilUpdateIsCalled();
    assertEquals("exampleRoom",
                 GameInstance.getInstance().getRoom("exampleRoom").getRoomId());
}