How to mock method before activity is created?

Question

I have an Activity

public class MyActivity extends ActionBarActivity {

    public int i;

    @Override
    protected void onCreate(final Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        i = getSomeInt();
    }

    protected int getSomeInt() {
        return 1; // here can be an api-request
    }

}

and i want to test it with robolectric 3.0 and mockito.

But i need to mock getSomeInt() methiod.

@RunWith(RobolectricGradleTestRunner.class)
@Config(constants = BuildConfig.class)
public class MyActivityTest {

    private MyActivity mActivity;

    @Before
    public void setUp() {

        mActivity = spy(Robolectric.buildActivity(MyActivity.class).create().get());
        doReturn(2).when(mActivity).getSomeInt(); //but it is already after onCreate!

    }

    @Test
    public void testGetInt() {
        assertEquals(2, mActivity.i); //error
    }
}

Is it possible to use already mocked method by creating of activity?

EDIT

i have tried

@Before
public void setUp() {
    ActivityController<MyActivity> co = Robolectric.buildActivity(MyActivity.class);
    mActivity = spy(co.get());
    doReturn(2).when(mActivity).getSomeInt();
    co.create();
}

but i seems, that onCreate was not called by mActivity

assertEquals(2, mActivity.i); //gives the result:

java.lang.AssertionError: 
Expected :2
Actual   :0

thanks Eugen for the consideration, it doesnt work, because create call on controller, that operates with activity that is not spied

Answer 1

Mockito only mocks an object. But it cannot modify the activity reference of ActivityController.

So I try to isolate the function and pass it to activity before creating.

Four steps:

1. Isolate the functions as a member of a new class

   public class SomeInt{
       public int get() {
           return 1; // here can be an api-request
       }
   }
   

2. Use the functions by an object in MyActivity

   public class MyActivity extends ActionBarActivity {
   
       SomeInt someInt;
   
       @Override
       protected void onCreate(final Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
   
           i = someInt.get();
       }
   }
   

   3. Make an API to set the object someInt in test

      • use ShadowActivity -- I recommanded this, separating the code and the test

        @Implements(MyActivity.class)
        public class ShadowMyActivity extends ShadowActivity
        {
            @RealObject
            private MyActivity myActivity;
        
            @Implementation
            public void setForMockito(SomeInt someint)
            {
                myActivity.someint = someint;
            }
        }
        

      • or let the object public

        public SomeInt someInt;

      • or make a public setter for the object in MyActivity

   4. Mock in test

      • If use ShadowActivity

        @Config(constants = BuildConfig.class shadows = ShadowMyActivity.class)
        Class TestMyActivity {
        
            @Before
            public void setUp()
            {
                SomeInt someIntMock = mock(SomeInt.class);
        
                ActivityController<MyActivity> co = Robolectric.buildActivity(MyActivity.class);
        
                mActivity.setForMockito(someIntMock);
        
                doReturn(2).when(someIntMock).get();
        
                co.create();
        
                // verify here or in tearDown
            }
        
            ...
        }