使用通用方法的Mockito

Question

I am trying to mock a generic method on my class with mockito but when the test code runs i always get a NullPointerException.

This is the class i want to mock.

public abstract class MyClass{
      public abstract <T> T find(T t);
}

My test code looks something like this.

@Mock private MyClass myClass;

public testOnReceive(){
             Mockito.when(
                myClass.find(Mockito.isA(BroadcastReceiver.class))).
                thenReturn(broadcastReceiver);

                myReceiver.onReceive(context,intent);

}

And finally the class i am trying to test is an extention of the BroadcastReceiver class and this is the code that i want to test

public class MyReceiver extendes BroadcastReceiver{
       public onReceive(Context context , Intent intent){
             ...
             ...
             myClass.find(this);
       }
}

The problem is with the mocking of the class. The class actually gets mocked(it is not null) but when the generic method is called then i get a null.

Any ideas?

Thank you

Answer 1

Here is a solution which should work for you, even if you have partial mocking (ie for some methods you want the real method to be invoked while sometimes you want the mock):

public class AbstractMethodMocker implements Answer<Object> {
    @Override
    public Object answer(InvocationOnMock invocation) throws Throwable
    {
        Answer<Object> answer;
        if (isAbstract(invocation.getMethod().getModifiers()))
            answer = RETURNS_DEFAULTS;
        else
            answer = CALLS_REAL_METHODS;
        return answer.answer(invocation);
    }
}

@Test
public void testOnReceive() {
    MyClass clazz = mock(MyClass.class, new AbstractMethodMocker());
    when(clazz.find(any(BroadcastReceiver.class)).thenReturn(broadcastReceiver);
    myReceiver.onReceive(context, intent);
}

Here is a great blog which discusses strategies of dealing with abstract classes (and their methods) using the Mockito framework.

Answer 2

My solution is similar to what Tim suggested but using a different kind of Answer object. Although i don't completely understand why but what worked for me was the following.

MyClass myClass = Mockito.mock(MyClass.class , Mockito.RETURNS_DEEP_STUBS);

After that i did not need to specify anything about when the method is called.