test.m

@RunWith(RobolectricGradleTestRunner.class)
public class MainActivityTest {

    @Inject CookieManager cookieManager;

    @Before
    public void setUp() {
        injectMocks(this);
    }

    // tests if the same instance is injected in test and in Activity
    @Test
    public void testInjection() throws Exception {
        assertEquals(cookieManager,
                buildActivity(MainActivity.class).create().get().cookieManager);
    }

    // tests if Activity is finishing if there's no cookie for vk.com
    @Test
    public void testLoggedOut() throws Exception {
        when(cookieManager.getCookie("vk.com")).thenReturn(null);
        assertTrue(buildActivity(MainActivity.class).create().get().isFinishing());
    }
}