test loader using robolectric

MainActivity

public class MainActivity extends FragmentActivity implements LoaderManager.LoaderCallbacks<String> {

    public boolean onCreateLoaderExecuted;
    public boolean onLoadFinishedExecuted;
    public boolean loadInBackgroundExecuted;


    @Override

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        getSupportLoaderManager().initLoader(0, null, this);

    }


    @Override
    public Loader<String> onCreateLoader(int i, Bundle bundle) {
        onCreateLoaderExecuted = true;
        return new AsyncTaskLoader<String>(this) {
            @Override
            public String loadInBackground() {
                loadInBackgroundExecuted = true;
                return "result";
            }
        };
    }

    @Override
    public void onLoadFinished(Loader<String> stringLoader, String s) {
        onLoadFinishedExecuted = true;

    }

    @Override
    public void onLoaderReset(Loader<String> stringLoader) {

    }
}

MainActivityTest

@RunWith(RobolectricTestRunner.class)
@Config(emulateSdk = 18)
public class MainActivityTest {

    @Test
    public void test() throws Exception {
        MainActivity mainActivity = Robolectric.buildActivity(MainActivity.class).create().start().resume().visible().get();
        assertTrue(mainActivity.onCreateLoaderExecuted);
        assertTrue(mainActivity.loadInBackgroundExecuted); //fail
        assertTrue(mainActivity.onLoadFinishedExecuted); //fail
    }

}