在 mockito 中使用 when().thenreturn() 时出现空指针异常
Getting a nullpointer exception when using when().thenreturn() in mockito
我使用下面的命令进行了 mockito junit 测试。变量 serviceTask 是一个名为 ServiceTask 的接口实例。我在声明中使用了@Mock
声明：
@Mock
private ServiceTask
命令行：
Mockito.when(serviceTask.getTask(Mockito.anyLong())).thenReturn(new Task());
堆栈跟踪：
java.lang.NullPointerException at
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:90)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:55)
at java.lang.reflect.Method.invoke(Method.java:508) 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.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at
org.mockito.internal.runners.DefaultInternalRunner.evaluate(DefaultInternalRunner.java:54)
at
org.junit.rules.ExpectedException$ExpectedExceptionStatement.evaluate(ExpectedException.java:239)
at org.junit.rules.RunRules.evaluate(RunRules.java:20) 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.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.junit.runners.ParentRunner.run(ParentRunner.java:363) at
org.mockito.internal.runners.DefaultInternalRunner.run(DefaultInternalRunner.java:99)
at
org.mockito.internal.runners.DefaultInternalRunner.run(DefaultInternalRunner.java:105)
at
org.mockito.internal.runners.StrictRunner.run(StrictRunner.java:40)
at
org.mockito.junit.MockitoJUnitRunner.run(MockitoJUnitRunner.java:163)
at
org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:89)
at
org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:41)
at
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:541)
at
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:763)
at
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:463)
at
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:209)
如果 NPE 发生在您上面提到的代码行 serviceTask，唯一的原因是 null。
如果您没有使用可以帮助您初始化模拟实例的正确测试运行器，那么您实际上可以在 setUp 方法中使用 MockitoAnnotations.initMocks(this);[=14 手动初始化它们=]
但是如果您已经这样做或使用了正确的测试运行器，那么您可能链接到了错误的代码行。自己再调试一下。
您的堆栈跟踪看起来不像是由您链接的代码行引起的。
我使用下面的命令进行了 mockito junit 测试。变量 serviceTask 是一个名为 ServiceTask 的接口实例。我在声明中使用了@Mock
声明：
@Mock
private ServiceTask
命令行：
Mockito.when(serviceTask.getTask(Mockito.anyLong())).thenReturn(new Task());
堆栈跟踪：
java.lang.NullPointerException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:90) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:55) at java.lang.reflect.Method.invoke(Method.java:508) 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.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26) at org.mockito.internal.runners.DefaultInternalRunner.evaluate(DefaultInternalRunner.java:54) at org.junit.rules.ExpectedException$ExpectedExceptionStatement.evaluate(ExpectedException.java:239) at org.junit.rules.RunRules.evaluate(RunRules.java:20) 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.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.junit.runners.ParentRunner.run(ParentRunner.java:363) at org.mockito.internal.runners.DefaultInternalRunner.run(DefaultInternalRunner.java:99) at org.mockito.internal.runners.DefaultInternalRunner.run(DefaultInternalRunner.java:105) at org.mockito.internal.runners.StrictRunner.run(StrictRunner.java:40) at org.mockito.junit.MockitoJUnitRunner.run(MockitoJUnitRunner.java:163) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:89) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:41) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:541) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:763) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:463) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:209)
如果 NPE 发生在您上面提到的代码行 serviceTask，唯一的原因是 null。
如果您没有使用可以帮助您初始化模拟实例的正确测试运行器，那么您实际上可以在 setUp 方法中使用 MockitoAnnotations.initMocks(this);[=14 手动初始化它们=]
但是如果您已经这样做或使用了正确的测试运行器，那么您可能链接到了错误的代码行。自己再调试一下。
您的堆栈跟踪看起来不像是由您链接的代码行引起的。