NullPointerException in java.lang.reflect.Method.getParameterTypes

Trying to upgrade Mockito from 3.4.6 (3.4.8 wasn’t published to Maven central) to anything 3.5.x (3.5.7 included) and I get some weird NPEs, which don’t happen if I run each test on its own:

[INFO] Running core.rest.exception.mapper.NotFoundExceptionMapperTest
07:22:56.767 [main] WARN  core.rest.exception.mapper.NotFoundExceptionMapper - Endpoint not found for path: http://host:8080/404
[ERROR] Tests run: 3, Failures: 0, Errors: 2, Skipped: 0, Time elapsed: 0.019 s <<< FAILURE! - in core.rest.exception.mapper.NotFoundExceptionMapperTest
[ERROR] testExceptionCreatesServerErrorResponseWhenEndpointWasNotMatchedAndIsServiceRequest  Time elapsed: 0.012 s  <<< ERROR!
java.lang.NullPointerException
        at java.base/java.lang.reflect.Method.getParameterTypes(Method.java:311)
        at org.mockito.internal.creation.DelegatingMethod.<init>(DelegatingMethod.java:20)
        at org.mockito.internal.invocation.DefaultInvocationFactory.createMockitoMethod(DefaultInvocationFactory.java:80)
        at org.mockito.internal.invocation.DefaultInvocationFactory.createInvocation(DefaultInvocationFactory.java:59)
        at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor.doIntercept(MockMethodInterceptor.java:58)
        at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor.doIntercept(MockMethodInterceptor.java:47)
        at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor$DispatcherDefaultingToRealMethod.interceptAbstract(MockMethodInterceptor.java:129)
        at org.mockito.codegen.HttpHeaders$MockitoMock$2122467463.getHeaderString(Unknown Source)
        at core.rest.exception.mapper.NotFoundExceptionMapper.isServiceRequest(NotFoundExceptionMapper.java:56)
        at core.rest.exception.mapper.NotFoundExceptionMapper.getResponseBuilder(NotFoundExceptionMapper.java:48)
        at core.rest.exception.mapper.NotFoundExceptionMapper.getResponseBuilder(NotFoundExceptionMapper.java:13)
        at core.rest.exception.mapper.BaseExceptionMapper.getResponse(BaseExceptionMapper.java:33)
        at core.rest.exception.mapper.BaseExceptionMapper.toResponse(BaseExceptionMapper.java:28)
        at core.rest.exception.mapper.NotFoundExceptionMapperTest.testExceptionCreatesServerErrorResponseWhenEndpointWasNotMatchedAndIsServiceRequest(NotFoundExceptionMapperTest.java:43)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

Initially I thought it might be caused by the new MockedStatic usage, but I’ve marked those classes with @Disable and the exceptions happen anyway and the test classes that are affected weren’t using MockedStatic anyway, so I’m not exactly sure how to investigate this further.

[McKratt]

@TimvdLippe In my case I’m mocking also my own classes and get the same NPE. What can we do to help you to solve this issue ?

I don’t know if it helps but in Java 15 I got this log :

[ERROR] getCurrentCallContext_should_return  Time elapsed: 0.001 s  <<< ERROR!
java.lang.NullPointerException: Cannot invoke "[Ljava.lang.Class;.clone()" because "this.parameterTypes" is null
	at ch.mobi.jap.context.callcontext.internal.DefaultCallContextManagerTest.getCurrentCallContext_should_return(DefaultCallContextManagerTest.java:91)

[TimvdLippe]

Unfortunately, Method is one of the classes that Mockito relies on internally for its behavior. Stubbing Method will therefore lead to undefined behavior. Additionally, it is advised not to mock classes you don’t own: https://github.com/mockito/mockito/wiki/How-to-write-good-tests#dont-mock-a-type-you-dont-own We are working on improving the user experience by working on a DoNotMock feature to avoid mocking classes/methods that are known to crash Mockito internals (#1833). Therefore, I am closing this as “Infeasible”. Apologies for the uninformative exception that is thrown.