java - 为什么 void 方法在模拟对象上得到 NullPointerException？

Question

我正在为我的 java 应用程序编写单元测试，该应用程序分析对 Stash 的提交，Stash 是一个类似于 Github 的 atlassian 应用程序。

我测试的方法是这个:

public List<Message> processEvent(RepositoryRefsChangedEvent event) {
    ArrayList<Message> commitList = new ArrayList<Message>();

    for (RefChange refChange : event.getRefChanges()) {
        LOGGER.info("checking ref change refId={} fromHash={} toHash={} type={}", refChange.getRefId(), refChange.getFromHash(),
                refChange.getToHash(), refChange.getType());

        if (refChange.getRefId().startsWith(REF_BRANCH)) {
            if (refChange.getType() == RefChangeType.ADD && isDeleted(refChange)) {
                LOGGER.info("Deleted a ref that never existed. This shouldn't ever occur.");
            }
            else if (isDeleted(refChange) || isCreated(refChange)) {
                branchCreation(refChange, event.getRepository(), commitList);
            }
            else {
                sepCommits.findCommitInfo(refChange, event.getRepository(), commitList);
            }
        }
        else {
            refNotProcessed(refChange);
        }
    }
    return commitList;
}

我试图确保如果我有一个 git notes 提交，处理将被忽略并调用 refNotProcessed(..)。

幸运的是，我能够相对轻松地解决这个问题并得出以下解决方案:

@RunWith (MockitoJUnitRunner.class)
public class RefChangEventTest {
    @Mock RefChange ref;
    @Mock RepositoryRefsChangedEvent refsChangedEvent;
    @Mock Repository repo;
    @Mock ApplicationPropertiesService appService;
    @Mock SEPCommits sepCommits;
    @Spy SEPRefChangeEventImpl sepRefChangeEvent = new SEPRefChangeEventImpl(sepCommits, appService);

    @Before
    public void testSetup() {
        Collection<RefChange> refList = new ArrayList<RefChange>(1);
        refList.add(ref);
        when(refsChangedEvent.getRefChanges()).thenReturn(refList);
        when(refsChangedEvent.getRepository()).thenReturn(repo);
    }

    @Test
    public void gitNotesAreIgnored() throws Exception {
        when(ref.getRefId()).thenReturn("refs/notes/foo");
        when(ref.getFromHash()).thenReturn("da69d7e202d7f66cba01c6f4030bd5975adbf200");
        when(ref.getToHash()).thenReturn("da69d7e202d7f66cba01c6f4030bd5975adbf201");
        doNothing().when(sepCommits).findCommitInfo(any(RefChange.class), any(Repository.class), any(ArrayList.class));

        sepRefChangeEvent.processEvent(refsChangedEvent);
        verify(sepRefChangeEvent, times(1)).refNotProcessed(ref);
    }

在此之后，我想看看如果我将 ref 名称更改为预期的名称(如 refs/heads/foo)，我的单元测试是否会因正确的原因而失败。我希望看到类似这样的内容:expected 1 execution of refNotProcessed but was not run at all

相反，我得到:

java.lang.NullPointerException
at com.cray.stash.SEPRefChangeEventImpl.processEvent(SEPRefChangeEventImpl.java:62)
at ut.com.isroot.stash.plugin.RefChangEventTest.gitNotesAreIgnored(RefChangEventTest.java:48)
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:497)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
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:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
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:160)
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:253)
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:497)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)

它指向对 sepCommits.findCommitInfo(..) 的调用 默认情况下，具有 void 签名的方法在模拟调用它们时不执行任何操作。这正是我想要它做的。我希望它被调用，但除了记录与 sepCommits 交互的事实外什么都不做。为什么会发生 NPE？

以下是人们要求的更多方法:

public SEPRefChangeEventImpl(SEPCommits sepCommits, ApplicationPropertiesService appService) {
    this.sepCommits = sepCommits;

    try {
        endpoint = appService.getPluginProperty("plugin.fedmsg.events.relay.endpoint");
    } catch (Exception e) {
        LOGGER.error("Failed to retrieve properties\n" + e);
    }

    if (endpoint == null) {
        endpoint = "tcp://some.web.address"
    }
}


public void refNotProcessed(RefChange refChange) {
    LOGGER.info("This type of refChange is not supported.\n refId={} fromHash={} toHash={} type={}", refChange.getRefId(), refChange.getFromHash(),
            refChange.getToHash(), refChange.getType());
}

public void findCommitInfo(RefChange ref, Repository repo, ArrayList<Message> commitList) {
    Page<Commit> commits = getChangeset(repo, ref);
    for (Commit commit : commits.getValues()) {
        String topic = topicPrefix + repo.getProject().getKey() + "." + repo.getName() + ".commit";
        Message message = new Message(getInfo(commit, ref), topic);
        commitList.add(message);
    }
}

Answer 1

从我在您的设置中看到的情况来看，sepCommits 是类中的依赖项，包含 processEvent() 方法。

您必须将您在测试中创建的模拟注入(inject)到 sepRefChangeEvent 变量中。通常这是通过在构造期间将其作为参数传递或通过 setter 方法来完成的。我在你的测试类中没有看到这样的代码。我认为你实际上是在击中一个真实的实例，而不是那里的模拟实例，这是导致异常的原因。