片段单元测试：launchFragment 抛出 ClassCastException
Fragment Unit Testing: launchFragment throws ClassCastException
我试图在我的单元测试中调用片段 class 中的方法，但我一直收到错误 java.lang.ClassCastException: androidx.fragment.app.testing.FragmentScenario$EmptyFragmentActivity cannot be cast to com.nu.rms.inspections.ui.activity.InspectionActivity
我正在关注 Google 的 docs。我很困惑为什么空片段 activity 试图转换为我的 InspectionActivity（片段所在的父 activity），也许这是预期的？
如何减轻 CastClassException 并在我的单元测试中使用我的片段方法？ ()
测试
@RunWith(AndroidJUnit4::class)
class ExampleUnitTest {
@Test
fun `inspection failure point to location mapping is correct`() {
val scenario = launchFragment<ContentFragment>()
scenario.onFragment { fragment ->
//TODO: test logic
}
}
...
}
片段Class
import androidx.fragment.app.Fragment
...
class ContentFragment : Fragment() {...}
堆栈跟踪
java.lang.ClassCastException: androidx.fragment.app.testing.FragmentScenario$EmptyFragmentActivity cannot be cast to com.nu.rms.inspections.ui.activity.InspectionActivity
at com.nu.rms.inspections.ui.fragment.ContentFragment.clearRFIDCache(ContentFragment.kt:565)
at com.nu.rms.inspections.ui.fragment.ContentFragment.showStep1(ContentFragment.kt:222)
at com.nu.rms.inspections.ui.fragment.ContentFragment.access$showStep1(ContentFragment.kt:37)
at com.nu.rms.inspections.ui.fragment.ContentFragment$onViewCreated.onChanged(ContentFragment.kt:77)
at com.nu.rms.inspections.ui.fragment.ContentFragment$onViewCreated.onChanged(ContentFragment.kt:37)
at androidx.lifecycle.LiveData.considerNotify(LiveData.java:113)
at androidx.lifecycle.LiveData.dispatchingValue(LiveData.java:131)
at androidx.lifecycle.LiveData.setValue(LiveData.java:289)
at androidx.lifecycle.MutableLiveData.setValue(MutableLiveData.java:33)
at androidx.lifecycle.Transformations.onChanged(Transformations.java:153)
at androidx.lifecycle.MediatorLiveData$Source.onChanged(MediatorLiveData.java:152)
at androidx.lifecycle.LiveData.considerNotify(LiveData.java:113)
at androidx.lifecycle.LiveData.dispatchingValue(LiveData.java:126)
at androidx.lifecycle.LiveData$ObserverWrapper.activeStateChanged(LiveData.java:424)
at androidx.lifecycle.LiveData.observeForever(LiveData.java:214)
at androidx.lifecycle.MediatorLiveData$Source.plug(MediatorLiveData.java:141)
at androidx.lifecycle.MediatorLiveData.addSource(MediatorLiveData.java:96)
at androidx.lifecycle.Transformations.onChanged(Transformations.java:150)
at androidx.lifecycle.MediatorLiveData$Source.onChanged(MediatorLiveData.java:152)
at androidx.lifecycle.LiveData.considerNotify(LiveData.java:113)
at androidx.lifecycle.LiveData.dispatchingValue(LiveData.java:126)
at androidx.lifecycle.LiveData$ObserverWrapper.activeStateChanged(LiveData.java:424)
at androidx.lifecycle.LiveData.observeForever(LiveData.java:214)
at androidx.lifecycle.MediatorLiveData$Source.plug(MediatorLiveData.java:141)
at androidx.lifecycle.MediatorLiveData.onActive(MediatorLiveData.java:118)
at androidx.lifecycle.LiveData$ObserverWrapper.activeStateChanged(LiveData.java:418)
at androidx.lifecycle.LiveData$LifecycleBoundObserver.onStateChanged(LiveData.java:376)
at androidx.lifecycle.LifecycleRegistry$ObserverWithState.dispatchEvent(LifecycleRegistry.java:361)
at androidx.lifecycle.LifecycleRegistry.forwardPass(LifecycleRegistry.java:300)
at androidx.lifecycle.LifecycleRegistry.sync(LifecycleRegistry.java:339)
at androidx.lifecycle.LifecycleRegistry.moveToState(LifecycleRegistry.java:145)
at androidx.lifecycle.LifecycleRegistry.handleLifecycleEvent(LifecycleRegistry.java:131)
at androidx.fragment.app.FragmentViewLifecycleOwner.handleLifecycleEvent(FragmentViewLifecycleOwner.java:51)
at androidx.fragment.app.Fragment.performStart(Fragment.java:2639)
at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:915)
at androidx.fragment.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManagerImpl.java:1238)
at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:1303)
at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:439)
at androidx.fragment.app.FragmentManagerImpl.executeOps(FragmentManagerImpl.java:2079)
at androidx.fragment.app.FragmentManagerImpl.executeOpsTogether(FragmentManagerImpl.java:1869)
at androidx.fragment.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManagerImpl.java:1824)
at androidx.fragment.app.FragmentManagerImpl.execSingleAction(FragmentManagerImpl.java:1696)
at androidx.fragment.app.BackStackRecord.commitNow(BackStackRecord.java:293)
at androidx.fragment.app.testing.FragmentScenario.perform(FragmentScenario.java:312)
at androidx.fragment.app.testing.FragmentScenario.perform(FragmentScenario.java:291)
at androidx.test.core.app.ActivityScenario.lambda$onActivity$ActivityScenario(ActivityScenario.java:534)
at androidx.test.core.app.ActivityScenario$$Lambda[=12=].run(Unknown Source)
at org.robolectric.android.fakes.RoboMonitoringInstrumentation.runOnMainSync(RoboMonitoringInstrumentation.java:53)
at androidx.test.core.app.ActivityScenario.onActivity(ActivityScenario.java:527)
at androidx.fragment.app.testing.FragmentScenario.internalLaunch(FragmentScenario.java:290)
at androidx.fragment.app.testing.FragmentScenario.launch(FragmentScenario.java:203)
at com.nu.rms.inspections.ExampleUnitTest.inspection failure point to location mapping is correct(ExampleUnitTest.kt:56)
at org.junit.runners.model.FrameworkMethod.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.robolectric.RobolectricTestRunner$HelperTestRunner.evaluate(RobolectricTestRunner.java:600)
at org.robolectric.internal.SandboxTestRunner.evaluate(SandboxTestRunner.java:260)
at org.robolectric.internal.SandboxTestRunner.runChild(SandboxTestRunner.java:130)
at org.robolectric.internal.SandboxTestRunner.runChild(SandboxTestRunner.java:42)
at org.junit.runners.ParentRunner.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access[=12=]0(ParentRunner.java:58)
at org.junit.runners.ParentRunner.evaluate(ParentRunner.java:268)
at org.robolectric.internal.SandboxTestRunner.evaluate(SandboxTestRunner.java:84)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at androidx.test.runner.AndroidJUnit4.run(AndroidJUnit4.java:104)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
FragmentScenario 将您的片段添加到一个空 activity class - 堆栈跟踪中提到的 androidx.fragment.app.testing.FragmentScenario$EmptyFragmentActivity。
这意味着您的 Fragment 在 InspectionActivity class 的实例中是 而不是 。您正在崩溃，因为您的 clearRFIDCache() 方法正在将 activity 转换为 InspectionActivity。
如果你想在 Activity 的特定实例中测试你的 Fragment 并且两者之间有很强的耦合，你需要使用 ActivityScenario 并手动将你的 Fragment 添加到那个 Activity，而不是使用 FragmentScenario，这让您无法控制您正在使用的 activity class。
理想情况下，您不应该 将您的 Fragment 与您的 Activity 紧密耦合。例如，您可以提供一个 FragmentFactory，它使用构造函数注入来添加您的 Fragment 所需的接口，而不是像 Fragments: Past, Present, and Future talk 中讨论的那样，您的 Fragment 达到 Activity 直接调用方法:
// Create an interface for what methods you want to expose
interface Inspector {
// whatever methods you want
}
// Change your Fragment to take in that interface
class ContentFragment(val inspector: Inspector) : Fragment() {
fun clearRFIDCache() {
// Now you can call methods on inspector here
// without casting your Activity
}
}
private class InspectionActivityFactory(
inspector: Inspector
) : FragmentFactory() {
override fun instantiate(
classLoader: ClassLoader,
className: String
) = when (className) {
ContentFragment::class.java.name -> ContentFragment(inspector)
else -> super.instantiate(classLoader, className)
}
}
// Now update your InspectionActivity to implement the interface
// and pass itself into an instance of the FragmentFactory you created
class InspectionActivity : AppCompatActivity(), Inspector {
override fun onCreate(savedInstanceState: Bundle?) {
supportFragmentManager.fragmentFactory =
InspectionActivityFactory(this)
super.onCreate(savedInstanceState)
...
}
}
launchFragment 接受一个 factory 参数，允许您注入一个测试接口，确保您可以检查是否获得了您期望的回调，而无需依赖特定的子class你的 activity。使用 Kotlin 时，您还可以使用尾随 lambda 语法来构造 Fragment，完全跳过手动创建 Factory：
@RunWith(AndroidJUnit4::class)
class ExampleUnitTest {
@Test
fun `inspection failure point to location mapping is correct`() {
val inspector = mock(Inspector::class.java)
val scenario = launchFragment {
ContentFragment(inspector)
}
scenario.onFragment { fragment ->
//TODO: test logic
}
}
...
}
我试图在我的单元测试中调用片段 class 中的方法，但我一直收到错误 java.lang.ClassCastException: androidx.fragment.app.testing.FragmentScenario$EmptyFragmentActivity cannot be cast to com.nu.rms.inspections.ui.activity.InspectionActivity
我正在关注 Google 的 docs。我很困惑为什么空片段 activity 试图转换为我的 InspectionActivity（片段所在的父 activity），也许这是预期的？
如何减轻 CastClassException 并在我的单元测试中使用我的片段方法？ (
测试
@RunWith(AndroidJUnit4::class)
class ExampleUnitTest {
@Test
fun `inspection failure point to location mapping is correct`() {
val scenario = launchFragment<ContentFragment>()
scenario.onFragment { fragment ->
//TODO: test logic
}
}
...
}
片段Class
import androidx.fragment.app.Fragment
...
class ContentFragment : Fragment() {...}
堆栈跟踪
java.lang.ClassCastException: androidx.fragment.app.testing.FragmentScenario$EmptyFragmentActivity cannot be cast to com.nu.rms.inspections.ui.activity.InspectionActivity
at com.nu.rms.inspections.ui.fragment.ContentFragment.clearRFIDCache(ContentFragment.kt:565)
at com.nu.rms.inspections.ui.fragment.ContentFragment.showStep1(ContentFragment.kt:222)
at com.nu.rms.inspections.ui.fragment.ContentFragment.access$showStep1(ContentFragment.kt:37)
at com.nu.rms.inspections.ui.fragment.ContentFragment$onViewCreated.onChanged(ContentFragment.kt:77)
at com.nu.rms.inspections.ui.fragment.ContentFragment$onViewCreated.onChanged(ContentFragment.kt:37)
at androidx.lifecycle.LiveData.considerNotify(LiveData.java:113)
at androidx.lifecycle.LiveData.dispatchingValue(LiveData.java:131)
at androidx.lifecycle.LiveData.setValue(LiveData.java:289)
at androidx.lifecycle.MutableLiveData.setValue(MutableLiveData.java:33)
at androidx.lifecycle.Transformations.onChanged(Transformations.java:153)
at androidx.lifecycle.MediatorLiveData$Source.onChanged(MediatorLiveData.java:152)
at androidx.lifecycle.LiveData.considerNotify(LiveData.java:113)
at androidx.lifecycle.LiveData.dispatchingValue(LiveData.java:126)
at androidx.lifecycle.LiveData$ObserverWrapper.activeStateChanged(LiveData.java:424)
at androidx.lifecycle.LiveData.observeForever(LiveData.java:214)
at androidx.lifecycle.MediatorLiveData$Source.plug(MediatorLiveData.java:141)
at androidx.lifecycle.MediatorLiveData.addSource(MediatorLiveData.java:96)
at androidx.lifecycle.Transformations.onChanged(Transformations.java:150)
at androidx.lifecycle.MediatorLiveData$Source.onChanged(MediatorLiveData.java:152)
at androidx.lifecycle.LiveData.considerNotify(LiveData.java:113)
at androidx.lifecycle.LiveData.dispatchingValue(LiveData.java:126)
at androidx.lifecycle.LiveData$ObserverWrapper.activeStateChanged(LiveData.java:424)
at androidx.lifecycle.LiveData.observeForever(LiveData.java:214)
at androidx.lifecycle.MediatorLiveData$Source.plug(MediatorLiveData.java:141)
at androidx.lifecycle.MediatorLiveData.onActive(MediatorLiveData.java:118)
at androidx.lifecycle.LiveData$ObserverWrapper.activeStateChanged(LiveData.java:418)
at androidx.lifecycle.LiveData$LifecycleBoundObserver.onStateChanged(LiveData.java:376)
at androidx.lifecycle.LifecycleRegistry$ObserverWithState.dispatchEvent(LifecycleRegistry.java:361)
at androidx.lifecycle.LifecycleRegistry.forwardPass(LifecycleRegistry.java:300)
at androidx.lifecycle.LifecycleRegistry.sync(LifecycleRegistry.java:339)
at androidx.lifecycle.LifecycleRegistry.moveToState(LifecycleRegistry.java:145)
at androidx.lifecycle.LifecycleRegistry.handleLifecycleEvent(LifecycleRegistry.java:131)
at androidx.fragment.app.FragmentViewLifecycleOwner.handleLifecycleEvent(FragmentViewLifecycleOwner.java:51)
at androidx.fragment.app.Fragment.performStart(Fragment.java:2639)
at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:915)
at androidx.fragment.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManagerImpl.java:1238)
at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:1303)
at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:439)
at androidx.fragment.app.FragmentManagerImpl.executeOps(FragmentManagerImpl.java:2079)
at androidx.fragment.app.FragmentManagerImpl.executeOpsTogether(FragmentManagerImpl.java:1869)
at androidx.fragment.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManagerImpl.java:1824)
at androidx.fragment.app.FragmentManagerImpl.execSingleAction(FragmentManagerImpl.java:1696)
at androidx.fragment.app.BackStackRecord.commitNow(BackStackRecord.java:293)
at androidx.fragment.app.testing.FragmentScenario.perform(FragmentScenario.java:312)
at androidx.fragment.app.testing.FragmentScenario.perform(FragmentScenario.java:291)
at androidx.test.core.app.ActivityScenario.lambda$onActivity$ActivityScenario(ActivityScenario.java:534)
at androidx.test.core.app.ActivityScenario$$Lambda[=12=].run(Unknown Source)
at org.robolectric.android.fakes.RoboMonitoringInstrumentation.runOnMainSync(RoboMonitoringInstrumentation.java:53)
at androidx.test.core.app.ActivityScenario.onActivity(ActivityScenario.java:527)
at androidx.fragment.app.testing.FragmentScenario.internalLaunch(FragmentScenario.java:290)
at androidx.fragment.app.testing.FragmentScenario.launch(FragmentScenario.java:203)
at com.nu.rms.inspections.ExampleUnitTest.inspection failure point to location mapping is correct(ExampleUnitTest.kt:56)
at org.junit.runners.model.FrameworkMethod.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.robolectric.RobolectricTestRunner$HelperTestRunner.evaluate(RobolectricTestRunner.java:600)
at org.robolectric.internal.SandboxTestRunner.evaluate(SandboxTestRunner.java:260)
at org.robolectric.internal.SandboxTestRunner.runChild(SandboxTestRunner.java:130)
at org.robolectric.internal.SandboxTestRunner.runChild(SandboxTestRunner.java:42)
at org.junit.runners.ParentRunner.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access[=12=]0(ParentRunner.java:58)
at org.junit.runners.ParentRunner.evaluate(ParentRunner.java:268)
at org.robolectric.internal.SandboxTestRunner.evaluate(SandboxTestRunner.java:84)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at androidx.test.runner.AndroidJUnit4.run(AndroidJUnit4.java:104)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
FragmentScenario 将您的片段添加到一个空 activity class - 堆栈跟踪中提到的 androidx.fragment.app.testing.FragmentScenario$EmptyFragmentActivity。
这意味着您的 Fragment 在 InspectionActivity class 的实例中是 而不是 。您正在崩溃，因为您的 clearRFIDCache() 方法正在将 activity 转换为 InspectionActivity。
如果你想在 Activity 的特定实例中测试你的 Fragment 并且两者之间有很强的耦合，你需要使用 ActivityScenario 并手动将你的 Fragment 添加到那个 Activity，而不是使用 FragmentScenario，这让您无法控制您正在使用的 activity class。
理想情况下，您不应该 将您的 Fragment 与您的 Activity 紧密耦合。例如，您可以提供一个 FragmentFactory，它使用构造函数注入来添加您的 Fragment 所需的接口，而不是像 Fragments: Past, Present, and Future talk 中讨论的那样，您的 Fragment 达到 Activity 直接调用方法:
// Create an interface for what methods you want to expose
interface Inspector {
// whatever methods you want
}
// Change your Fragment to take in that interface
class ContentFragment(val inspector: Inspector) : Fragment() {
fun clearRFIDCache() {
// Now you can call methods on inspector here
// without casting your Activity
}
}
private class InspectionActivityFactory(
inspector: Inspector
) : FragmentFactory() {
override fun instantiate(
classLoader: ClassLoader,
className: String
) = when (className) {
ContentFragment::class.java.name -> ContentFragment(inspector)
else -> super.instantiate(classLoader, className)
}
}
// Now update your InspectionActivity to implement the interface
// and pass itself into an instance of the FragmentFactory you created
class InspectionActivity : AppCompatActivity(), Inspector {
override fun onCreate(savedInstanceState: Bundle?) {
supportFragmentManager.fragmentFactory =
InspectionActivityFactory(this)
super.onCreate(savedInstanceState)
...
}
}
launchFragment 接受一个 factory 参数，允许您注入一个测试接口，确保您可以检查是否获得了您期望的回调，而无需依赖特定的子class你的 activity。使用 Kotlin 时，您还可以使用尾随 lambda 语法来构造 Fragment，完全跳过手动创建 Factory：
@RunWith(AndroidJUnit4::class)
class ExampleUnitTest {
@Test
fun `inspection failure point to location mapping is correct`() {
val inspector = mock(Inspector::class.java)
val scenario = launchFragment {
ContentFragment(inspector)
}
scenario.onFragment { fragment ->
//TODO: test logic
}
}
...
}