android - UnitTest 中 MutableLiveData 的 setValue 和 postValue

Question

我尝试在我的应用程序上测试一些方法，但在调用 mutablelivedata.postValue 时出现错误。这是一个 fragment 和错误消息:

@Test
public void callStartScreenRepository(){
    Observer<User> userObserver = mock(Observer.class);
    startScreenViewModel.returnUser().observeForever(userObserver);
    maennlich = new User();
    maennlich.setVorname("Christian");
    MutableLiveData<User> userTest = new MutableLiveData<>();
    userTest.postValue(maennlich);
    when(startScreenRepository.userWebService("testUser")).thenReturn(userTest);
    verify(userObserver).onChanged(maennlich);
}

java.lang.RuntimeException:未模拟 android.os.Looper 中的方法 getMainLooper。参见 http://g.co/androidstudio/not-mocked了解详情。

at android.os.Looper.getMainLooper(Looper.java)
at android.arch.core.executor.DefaultTaskExecutor.postToMainThread(DefaultTaskExecutor.java:48)
at android.arch.core.executor.AppToolkitTaskExecutor.postToMainThread(AppToolkitTaskExecutor.java:100)
at android.arch.lifecycle.LiveData.postValue(LiveData.java:277)
at android.arch.lifecycle.MutableLiveData.postValue(MutableLiveData.java:28)
at com.example.cfrindt.foodtracking.ViewModels.StartScreenViewModelTest.callStartScreenRepository(StartScreenViewModelTest.java:102)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.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.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:117)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:262)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:84)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)

无论我使用 setValue() 还是 postValue()，我都会收到此错误。我怎样才能让它发挥作用？

Answer 1

首先，您需要使用 InstantTaskExecutorRule，这意味着:

@Rule public InstantTaskExecutorRule instantExecutorRule = new InstantTaskExecutorRule();

这将允许立即使用 MutableLiveData。请记住在您的应用程序的 build.gradle 中包含导入:

testCompile "android.arch.core:core-testing:$rootProject.ext.arch_version"

然后，您需要使用覆盖 RxSchedulers 的规则定义 JUnit 规则，或者在 @Before 中使用 RxAndroidPlugins 覆盖调度程序(如果您使用的是 RxJava)

RxSchedulersOverrideRule:

public class RxSchedulersOverrideRule implements TestRule {
    @Override public Statement apply(final Statement base, Description description) {
    return new Statement() {
        @Override public void evaluate() throws Throwable {
            RxAndroidPlugins.reset();
            RxAndroidPlugins.setMainThreadSchedulerHandler(scheduler -> Schedulers.trampoline());

        RxJavaPlugins.reset();
        RxJavaPlugins.setIoSchedulerHandler(scheduler -> Schedulers.trampoline());
        RxJavaPlugins.setComputationSchedulerHandler(scheduler -> Schedulers.trampoline());
        RxJavaPlugins.setNewThreadSchedulerHandler(scheduler -> Schedulers.trampoline());

        base.evaluate();

        RxAndroidPlugins.reset();
        RxJavaPlugins.reset();
      }
    };
  }
}

并在测试类中调用它:

@Rule public RxSchedulersOverrideRule rxSchedulersOverrideRule = new RxSchedulersOverrideRule();

另一个选项是在 @Before 的 setup() 中调用:

RxAndroidPlugins.setInitMainThreadSchedulerHandler(schedulerCallable -> Schedulers.trampoline());

使用后需要在@After 的 tearDownClass() 中重置:

RxAndroidPlugins.reset();