android - 使用改造和 Rx android 进行单元测试

Question

我是单元测试的新手，我正在使用 rx android 进行单元测试改造。我有一个 observable，它从 api 获取访问 token ，我使用它通过改造来发送请求。由于它，我得到空指针异常这是我的代码:

@RunWith(MockitoJUnitRunner.class)
public class AuthenticationTokenGetterTest {
    @Mock
    AuthenticatorInterface authenticatorservice;
    @InjectMocks
    AuthenticationTokenGetter tokengetter;

    @Test
    public void testtokkengetter() {
        when(authenticatorservice.servicecall(anyString(), anyString())).thenReturn(
                Observable.just("44fffffggggggg"));

        Observable<String> obs = tokengetter.getToken();
        TestSubscriber<String> testsubscriber = new TestSubscriber<>();
        obs.subscribe(testsubscriber);
        testsubscriber.assertNoErrors(); // Here I get exception
        List<String> value = testsubscriber.getOnNextEvents();
    }

}

但我一直收到 java.lang.NullPointerException。我正在测试的可观察代码:

@CheckResult
    public Observable<String> getToken() {
        return service.servicecall(key, code)
                .subscribeOn(Schedulers.newThread())
                .doOnNext(new Action1<String>() {
                    public void call(String token) {
                        savedToken = token;
                    }
                })
                .observeOn(AndroidSchedulers.mainThread());
    }

我的错误是:

java.lang.AssertionError: Unexpected onError events: 1

    at rx.observers.TestSubscriber.assertNoErrors(TestSubscriber.java:308)
    at AuthenticationTokenGetterTest.testtokkengetter(AuthenticationTokenGetterTest.java:47)
    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.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$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.mockito.internal.runners.JUnit45AndHigherRunnerImpl.run(JUnit45AndHigherRunnerImpl.java:37)
    at org.mockito.runners.MockitoJUnitRunner.run(MockitoJUnitRunner.java:62)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:117)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:262)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:84)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
Caused by: java.lang.NullPointerException
    at rx.android.schedulers.LooperScheduler$HandlerWorker.schedule(LooperScheduler.java:77)
    at rx.android.schedulers.LooperScheduler$HandlerWorker.schedule(LooperScheduler.java:91)
    at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber.schedule(OperatorObserveOn.java:190)
    at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber$1.request(OperatorObserveOn.java:147)
    at rx.Subscriber.setProducer(Subscriber.java:209)
    at rx.Subscriber.setProducer(Subscriber.java:205)
    at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber.init(OperatorObserveOn.java:141)
    at rx.internal.operators.OperatorObserveOn.call(OperatorObserveOn.java:75)
    at rx.internal.operators.OperatorObserveOn.call(OperatorObserveOn.java:40)
    at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:46)
    at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:30)
    at rx.Observable.subscribe(Observable.java:8759)
    at rx.Observable.subscribe(Observable.java:8726)
.AuthenticationTokenGetterTest.testtokkengetter(AuthenticationTokenGetterTest.java:45)

Answer 1

您正在使用依赖于 Android Looper 类的 AndroidSchedulers.mainThread()，这就是空指针的原因。不要创建使用多线程的单元测试，在同一线程上执行所有内容!

您可以通过执行调度程序注入(inject)来解决此问题。您的 AuthenticationTokenGetter 类应该通过在构造函数中传递的 Scheduler 引用获取 mainThreadScheduler 实例，因此在您的正常代码中，您应该使用 mainThreadScheduler 创建对象 并在测试期间使用同步执行所有内容的 Scheduler 实现创建您的对象。

您还可以使用 RxJava/RxAndroidSchedulersHook 来覆盖调度程序。

@编辑一些解释如何注入(inject)/ovveride 调度程序的文章:

https://medium.com/@peter.tackage/overriding-rxandroid-schedulers-in-rxjava-2-5561b3d14212

https://medium.com/@peter.tackage/an-alternative-to-rxandroidplugins-and-rxjavaplugins-scheduler-injection-9831bbc3dfaf

这两种解决方案都有其优点和缺点，即使这些文章针对的是 RxJava2，这种方法对于 RxJava1 仍然有效(但是调度程序 Hook /插件在 Rx2 中的工作方式略有不同)