Robolectric 开始一个有观察者的片段

Question

如何在 Robolectric

的测试范围内启动带有 LiveData 观察器的片段

片段

class MyFragment(private val viewModel: MyViewModel) : Fragment() {

    ...

    fun myObserver {
        ... 
        // If I remove this observer the test will pass. 
        viewModel.MyLiveData.observe(viewLifecycleOwner, Observer{
            ...
        }
    }
}

我的测试使用 RobolectricTestRunner，因此我可以在测试范围内启动片段。

@RunWith(robolectricTestRunner::class) 
class MyFragmentTest {

    // Executes tasks in the Architecture Components in the same thread
    @get:Rule
    var instantTaskExecutorRule = InstantTaskExecutorRule()

    @Test
    fun testOne() {
        val viewModel: MyViewModel = mock(MyViewModel::class.java)
        val scenario = launchFragmentInContainer(
            factory = MainFragmentFactory(viewModel),
            fragmentArgs = null
            themeResId = R.style.Theme_MyTheme
        )
        // Tried implementing shadowOf as the error suggests. 

    } 
}

我在尝试运行测试时遇到以下错误。我已经尝试在实例化 FragmentScenario 之前和之后将 Main looper 设置为空闲。

java.lang.Exception: Main looper has queued unexecuted runnables. This might be the cause of the test failure. You might need a shadowOf(getMainLooper()).idle() call.

我试过以下方法

为 Main Looper 实现阴影 class。使用 Looper 模式注释 class。

@RunWith(RobolectricTestRunner::class)
@LooperMode(LooperMode.Mode.PAUSED)
class MyFragmentTest {

添加场景状态

    scenario.moveToState(Lifecycle.State.CREATED)
    scenario.moveToState(Lifecycle.State.RESUMED)

我的测试依赖项。

    // Test
    testImplementation 'androidx.arch.core:core-testing:2.1.0'
    testImplementation 'org.jetbrains.kotlinx:kotlinx-coroutines-test:1.4.3'
    testImplementation "androidx.test.ext:junit-ktx:1.1.2"
    testImplementation "org.jetbrains.kotlinx:kotlinx-coroutines-test:1.4.3"
    testImplementation 'com.nhaarman.mockitokotlin2:mockito-kotlin:2.2.0'
    testImplementation 'junit:junit:4.13.2'
    testImplementation 'androidx.test.espresso:espresso-core:3.3.0'
    testImplementation "org.robolectric:robolectric:4.5.1"
    testImplementation "org.mockito:mockito-android:2.28.2"

    // Testing Fragments
    debugImplementation "androidx.fragment:fragment-testing:1.3.2"

我用来寻找解决方案的链接' Testing LiveData Transformations? https://jeroenmols.com/blog/2019/01/17/livedatajunit5/

Answer 1

我查看了您在 github here 上的存储库。这是我的发现。

问题 1

你的第一个问题是你模拟了一个ViewModel。因此，当您为 Fragment 模拟 onResume 时，它会调用：

fun liveDataObserver() {
    viewModel.scoreLiveData.observe(viewLifecycleOwner, {
        // 
    } )
}

由于 viewModel 是模拟的，scoreLiveData 是 null 并且你得到一个 NPE。

要解决此问题，您还要模拟 scoreLiveData 方法，以便它 returns 一些可接受的结果：

...
    val liveData = MutableLiveData<Int>().apply { value = 3 }
    val viewModel = mock(MyViewModel::class.java)
    doReturn(liveData).`when`(viewModel).scoreLiveData
...

这将完全修复您的 testOne，但尚未 testTwo。

问题 2

它只与您的 testTwo 方法有关。问题是您在 also 块中调用 liveDataObserver()，并且在 Fragment's viewLifecycleOwner 已在 onCreateView 中设置之前被调用：

...
    scenario = launchFragmentInContainer {
        MyFragment(viewModel).also {
            it.liveDataObserver()
        }
    } 
...

我不确定你到底想在这里测试什么，但如果你想验证你可以在 Fragment's View 创建后开始观察，你可以做一些事情如下：

    ...
    // make sure your Fragment is started
    scenario = launchFragmentInContainer (
        factory = MainFragmentFactory(viewModel),
        initialState = Lifecycle.State.STARTED
    )
    // call liveDataObserver on it
    scenario.withFragment {
        this.liveDataObserver()
    }

完整代码

@RunWith(RobolectricTestRunner::class) class我的片段测试{ 私有 lateinit var 场景：FragmentScenario

@Test
fun testOne() = runBlockingTest {
    val liveData = MutableLiveData<Int>().apply { value = 1 }
    val viewModel = mock(MyViewModel::class.java)
    doReturn(liveData).`when`(viewModel).scoreLiveData

    scenario = launchFragmentInContainer(
        factory = MainFragmentFactory(viewModel),
        fragmentArgs = null,
        themeResId = R.style.Theme_TDDScoreKeeper,
        initialState = Lifecycle.State.STARTED
    )

    scenario.moveToState(Lifecycle.State.RESUMED)
    scenario.recreate() // Simulates if the phone ran low on resources and the app had to be recreated.
}

@Test
fun testTwo() {
    val liveData = MutableLiveData<Int>().apply { value = 1 }
    val viewModel = mock(MyViewModel::class.java)
    doReturn(liveData).`when`(viewModel).scoreLiveData

    scenario = launchFragmentInContainer(
        factory = MainFragmentFactory(viewModel),
        initialState = Lifecycle.State.STARTED
    )
    scenario.withFragment {
        this.liveDataObserver()
    }
}

}

Robolectric 开始一个有观察者的片段

Robolectric start a fragment that has an observer

android

android-livedata

robolectric

android-unit-testing

android-fragmentscenario

问题 1

问题 2

完整代码