Mockito/Power Mockito : unable to get expected output when mocking method of LayoutParams in android

Question

I have a method:

public class MarginConverter {
    int top = 0;
    int bottom = 0;
    int right = 0;
    int left = 0; 
    public MarginConverter(String val){
       top = bottom = right = left = Integer.parseInt(val);
    }

    public LayoutParams getLayoutParamsFromView(View view){
        LayoutParams layoutParams = (LayoutParams) view.getLayoutParams();
        int height, width;
        if (layoutParams == null) {
            height = LayoutParams.WRAP_CONTENT;
            width = LayoutParams.MATCH_PARENT;
            layoutParams = new LayoutParams(width, height);
            layoutParams.setMargins(left, top, right, bottom);
        } else {
            layoutParams.setMargins(left, top, right, bottom);
        }
        return layoutParams;
        }
    }

Note: Variables left, top, right, bottom are instance variables initialized on constructor call.

I want to test this method. I have mocked view.getLayoutParams() method. Method setMargin(int, int, int,int) is not setting margin parameters as mentioned and I am getting all parameters of LayoutParams(leftMargin, rightMargin, topMargin, bottomMargin) 0.0 in test though it's working correctly in code. What should I do so that I will get values as expected.

Please help me ! Any help will be appreciated..

This is my testCase code:

@RunWith(PowerMockRunner.class)
@PrepareForTest({ViewGroup.LayoutParams.class})
public class MarginConverterTest {
@Mock
private View view = mock(TextView.class);

private int left = 0;
private int right = 0;
private int top = 0;
private int bottom = 0;

@Before
public void setUp() throws Exception {
    when(view.getLayoutParams()).thenReturn(null);
}

/**
 * tests output for margin conversion when one argument is given
 */
@Test
public void test_OneArgumentMarginConversion(){
    left =top = right = bottom = 5;
    MarginConverter marginConverter = new marginConverter("5");
    LayoutParams params = marginConverter.getLayoutParamsFromView(view);
    Object[] marginArray = new Object[4];
    marginArray[0] = params.leftMargin;
    marginArray[1] = params.topMargin;
    marginArray[2] = params.rightMargin;
    marginArray[3] = params.bottomMargin;
    Assert.assertArrayEquals(new Object[]{left,top,right,bottom}, marginArray);
}
}

Answer 1

You seem to be confused about concept of mocking. If you mock something, it means its a dummy ( not real object ) and all of its method calls are fake.

If you wish margins to be non-zero , LayoutParams(leftMargin, rightMargin, topMargin, bottomMargin) , don't mock view or setMargin method.

If your view object is not real ( mocked , dummy etc ), your layoutParams is a fake one too ( means unknown values ) unless you are returning an actual layoutParams by using some mocking framework.

In simple terms, if you wish to set margins by calling setMargins , don't mock setMargins method call and make sure that layoutParams is not fake one.

Also, in your case if view is mocked, condition if (layoutParams == null) will never be satisfied as layoutParams will be a non - null fake object.

Solution - use an appropriate mocking method on call view.getLayoutParams() to return an appropriate real layoutParams object or null to satisfy both branches of code , if as well as else.

Hope it helps and let me know if I misunderstood your question.