ContextCompat with Mockito NullPointerException

Question

I am using mockito to unit test my viewmodel, however im getting a NullPointerException with ContextCompat.

@RunWith(MockitoJUnitRunner.class) 
public class ViewModelUnitTest {    
    @Mock 
    private MockContext mockContext;
    private ViewModel pViewModel; 

    @Before
    public void setup() {
        MockitoAnnotations.initMocks(this);
    }

    @Test
    public void testCProfile() throws Exception {
        Profile cProfile = GeneratorAPI.getCProfile();
        pViewModel = new ViewModel(cProfile, mockContext);

        assertEquals(View.GONE, pViewModel.userVisibilty.get());
       }
    }
}

//ViewModel

public ViewModel(Profile profile, Context context) {
    this.profile = profile;
    this.context = context;


    this.userTitleColor = new ObservableInt(ContextCompat.getColor(context, R.color.black));

    this.userVisibilty = new ObservableField<>();
}

However Im getting the following error with the ContextCompat :

java.lang.NullPointerException
at android.support.v4.content.ContextCompat.getColor(ContextCompat.java:411)
at ...ViewModel.<init>(ViewModel.java:102)
at ....ViewModelUnitTest. testCProfile(ViewModelUnitTest.java:60)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at ..

Thanks in advance

Answer 1

This what I did when I face this issue. Modified your test file as follows.

@RunWith(MockitoJUnitRunner.class) 
public class ViewModelUnitTest {    
    @Mock 
    private MockContext mockContext;
    private ViewModel pViewModel; 
    private Resources mockResources;

    @Before
    public void setup() {
        MockitoAnnotations.initMocks(this);
        when(mockContext.getResources()).thenReturn(mockResources)
        when(mockResources.getColor(anyInt(), any())).thenReturn(anyInt())
    }

    @Test
    public void testCProfile() throws Exception {
        Profile cProfile = GeneratorAPI.getCProfile();
        pViewModel = new ViewModel(cProfile, mockContext);

        assertEquals(View.GONE, pViewModel.userVisibilty.get());
    }
}

Explanation: ContextCompat.getColor() API call appropriate Context API to get the color id. So we have to mock those API calls to avoid the NPE.