Mock rest API call using Robolectric

Hi guys I am new to Unit testing Robolectric and Mockito.

How do you code so that your Rest api calls will use mock data when running unit test?

Inside my StockFragment.java, I use SpringAndroid + Robospice to perform a Rest Api call.

Also I have a RequestListener(from Robospice) inside the fragment that updates the UI in the fragment if the request is successful or not.

Here is my fragment:

   public class StockFragment extends RoboDialogFragment {

    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.my_layout, container, false);
        return view;
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        displayStockInfo();
    }

    private void displayStockInfo(){
        request = new MyRequest();
        request.setQuote(getStock().getSymbol());
        lastRequestCacheKey = request.createCacheKey();
        ((BaseActivity)getActivity()).getSpiceManager().execute(request, lastRequestCacheKey, DurationInMillis.ALWAYS_EXPIRED, new MyRequestListener());
    }

    private class MyRequestListener implements RequestListener<PseStocksResponse> {
        @Override
        public void onRequestFailure(SpiceException e) {
            //show toast about failure reason ...
        }
        @Override
        public void onRequestSuccess(PseStocksResponse pseStocksResponse) {
            //UPDATE UI VIEWS ...
        }
    }
}

Here is my Robolectric Test class.

   public class StockFragmentTest {
    MyRequest request;
    Stock stock;
    StockFragment stockFragment;

    @Before
    public void setUp(){
        stockFragment = new StockFragment();
        FragmentTestUtil.startFragment(stockInfoFragment);
        FragmentTestUtil.startVisibleFragment(stockInfoFragment);
        findViews();
    }

    public void findViews(){
        quoteTextView = (TextView)stockInfoFragment.getView().findViewById(R.id.quoteTextView);
        nameTextView = (TextView)stockInfoFragment.getView().findViewById(R.id.nameTextView );
        ...
    }

    @Test
    public void viewShouldNotBeNull(){
        assertNotNull(quoteTextView);
        assertNotNull(nameTextView);
        ...
    }

    @Test
    public void showDisplayedInfo(){
        //TODO: Assert textview.getText() values here
    }
}

One solution I am thinking is have testMode flag in the StockFragment and do some conditional statements that will return test data if true, but I think there is a better way to test.

I think I need to listen to Http requests on my Test class and catch that request then provide mock data, Im not sure though.