MainActivityTests.java

@RunWith(AndroidJUnit4.class)
public class MainActivityTests {

    @Rule
    public ActivityTestRule<MainActivity> activityRule =
            new ActivityTestRule<>(MainActivity.class);


    @Before
    public void init() {
        //getting the application class
        MyAppApplication myApp = (MyAppApplication) InstrumentationRegistry
                                .getInstrumentation()
                                .getTargetContext()
                                .getApplicationContext();
        
        //building the app component with the mocked module
        MyAppComponent mockedComponent = DaggerMyAppComponent.builder()
                                        .myAppModule(new MyAppModuleMock()).build();
        
        //setting the component with the mocked module as the main app component 
        myApp.setMyAppComponent(mockedComponent);
    }

    @Test
    public void getUsers() throws Exception {


        List<Object> users = activityRule.getActivity().getUsersFromNetwork();
        /// those are the mocked users....

    }
}