How to test a void method using Mockito

Question

the below posted method in the code section returns void. I want to know how to test a method that returns void. I checked some answers but the use "doThrow()" with passing an exception, but in my case the method does not throw any exception

please let me know how can I test a method returns void?

code

public void setImageOnImageView(RequestCreator requestCreator, ImageView imgView) {
    requestCreator.into(imgView);
}

testing:

public class ValidationTest {
    @Mock
    private Context mCtx = null;
    @Rule
    public MockitoRule mockitoRule = MockitoJUnit.rule();

    @Before
    public void setUp() throws Exception {
        mCtx = Mockito.mock(Context.class);
        Assert.assertNotNull("Context is not null", mCtx);
    }

    @Test
    public void setImageOnImageView() throws Exception {
        Uri mockUri = mock(Uri.class);
        RequestCreator requestCreator = Picasso.with(mCtx).load(mockUri);
        RequestCreator spyRequestCreator = spy(requestCreator);
        ImageView imageView = new ImageView(mCtx);
        ImageView spyImageView = spy(imageView);

        doThrow().when(spyRequestCreator).into(spyImageView);
        //spyRequestCreator.into(spyImageView);
    }
}

Answer 1

What exactly are you trying to test? Is that test that "when setImageOnImageView(RequestCreator, ImageView) is called, it invokes RequestCreator.into(ImageView)"?

If that's what you're trying to test, you aren't wanting to test that it "returns void". Rather, I would recommend something like:

@Test
public void itInvokesRequestCreatorIntoOnProvidedImageView() {
    RequestCreator creator = mock(RequestCreator.class);
    ImageView imageView = mock(ImageView.class);

    setImageOnImageView(creator, imageView);
    verify(creator).into(imageView);
}