Mockito - weird package scope class inheritance issue

Question

Found very interesting issue and after debugging found the scenario to reproduce it.

So, if I have a class with package scope B that has some public method and public class A that extends it:

package somepackage;

class B {
   public void someMethod() {
      throw NullPointerException();
   }
}

package somepackage;
public class A extends B {

}

and then in the test:

A a = mock(A.class);
a.someMethod();

and guess what, I am getting NullPointerException that I just threw, so Mockito somehow creates a "real" object and calls a real method instead of mocked one. Why so?

java.lang.IllegalArgumentException
    at test.B.setProxy(B.java:6)
    at test.A.setProxy(A.java:1)
    at secretservice.service.TestFDSServiceImpl.testService(TestFDSServiceImpl.java:17)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

In the example above I have IllegalArgumentException as I changed it in class B just to make sure NullPointerException is not caused by something else.

Eclipse: Juno Service Release 1, build id: 20120920-0800 Mockito: 1.8.4 (also tested with 1.9.5) JUnit: 4.10

it's class test.A$$EnhancerByMockitoWithCGLIB$$edd8e028 so I assume it just not able to mock the public method from package scope class — potomok, Dec 02 '13 at 14:53
Your mock object is not complete. You should use `when()` to give it some behavior. — Moritz Petersen, Dec 02 '13 at 14:54
Really? Why it's not complete? To my understanding it should call the dumb mocked method, but it calls a real why. If I do that, this method still will be called... Btw, If I change the scope of B to public, everything works as expected — potomok, Dec 02 '13 at 14:57
Hm. I just tried your example, and it works for me without throwing NPE... — Moritz Petersen, Dec 02 '13 at 14:59
Ok, cool, so it's fixed. What is your mockito version? Mine is 1.8.4 — potomok, Dec 02 '13 at 15:00
I just tried with 1.9.5, I still have the same exception. Btw, did you locate your test in a different package, I assume? So the B class is not visible to the Test — potomok, Dec 02 '13 at 15:02
Nope, still no problem here. I mean: `B` is not visible to `ATest`, and I don't get a NPE. — Moritz Petersen, Dec 02 '13 at 15:05
really strange, i updated the question with the exception I have :( — potomok, Dec 02 '13 at 15:09
Oops, sorry, in my example I just wanted to make sure that NullPointer is not caused by something else, so I changed it to illegal state, i will update the question now. Btw, did you test with junit or something else? — potomok, Dec 02 '13 at 15:10

bric3 · Accepted Answer · 2016-02-24T09:27:05.853

edit

Latest mockito 2.x beta use now ByteBuddy which isn't affected by this issue. There may be some API ajustements left but it is pretty much both working and functional. Also there will be breaking compatibility with existing mockito matchers. If that's ok for the project that would be great to have feedback on the API while mockito 2 is in beta.

original

There's a known issue when the mocked class have a non public parent. The method cannot be stubbed. See issue 212.

The issue is that bridge methods are generated by the compiler in order to access the method from the parent, however this confuses bytecode tools like CGLIB. Unless you can fix CGLIB, there's no real solution.

Sorry you have to workaround this in a different way :/

Thanks for this, yeap, I decided to go for very dumb solution, just creating one more class that inherits from the public class and overrides all not implemented methods, fortunately, in my case they are just setters — potomok, Dec 02 '13 at 16:11

Mockito - weird package scope class inheritance issue

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