android - 如何测试 SingleLiveEvent 变量？

Question

我有一个 SingleLiveEvent<Void>多变的。从 api 获得响应后，我将其发布。我的回调被调用并显示一个弹出窗口。我的问题是我将如何编写测试用例来检查我的弹出窗口是否显示。

现场 Activity :

private SingleLiveEvent<Void> onAccountOverDrawn = new SingleLiveEvent<>();

成功响应我打电话:

onAccountOverDrawn.post();

在我的 fragment 中，我将其注册为

viewModel.getOnAccountOverDrawn().observe(this, aVoid -> onAccountOverDrawn());

并在onAccountOverDrawn()我只是显示一个弹出窗口。

那么我将如何为这个场景编写测试用例？

当前测试用例:

@Test
public void updateApplicationStatus_AccountOverdrawn() {
    viewModel.updateApplicationStatus("AMOUNT_PENDING");

    assertNotNull(viewModel.getOnAccountOverDrawn()); //this line is of no use. Need to change this.
}

Answer 1

我这样解决这个问题:

1. 获取 LiveData 并为我们的模拟观察者订阅它。
2. 调用应更改 ViewModel 内的 LiveData 的方法。
3. 检查我们的模拟观察者是否收到了更新的数据。
4. 检查这个模拟观察者没有更多变化。
5. 检查如果我们在同一个 LiveData 上重新订阅这个模拟观察者，那么我们不会收到数据

见下面的代码:

@RunWith(MockitoJUnitRunner.class)
public class SomeFeatureViewModelTest {

    private SomeFeatureViewModel mSomeFeatureViewModel;

    // Rule for help testing. Just trust me you need it :)
    @Rule
    public InstantTaskExecutorRule mRule = new InstantTaskExecutorRule();

    @Mock
    private Observer<Void> mOnClickButtonEventObserver;

    @Before
    public void setup() {
        mSomeFeatureViewModel = new SomeFeatureViewModel();
    }

    @Test
    public void clickOnNextScreenButton() {

        // get LiveData and subscribe our observer to it:
        mSomeFeatureViewModel.getOnClickButtonEvent().observeForever(mOnClickButtonEventObserver);

        // call the method that should change the LiveData inside the ViewModel:
        mSomeFeatureViewModel.clickOnNextScreenButton();

        // check that our observer received the updated data:
        verify(mOnClickButtonEventObserver).onChanged(null);

        // check that there were no more changes of this observer:
        verifyNoMoreInteractions(mOnClickButtonEventObserver);

        // check that if we re-subscribe this observer on the same LiveData then we do not receive data:
        mSomeFeatureViewModel.getOnClickButtonEvent().observeForever(mOnClickButtonEventObserver);
        verifyNoMoreInteractions(mOnClickButtonEventObserver);

    }

}