redux-pre-thunk.js

// snip for production
const store = createStore(thunk.withExtraArgument({fetch}));

// snip effect
import { createAction } from 'redux-actions';

const createEffect = (name, fun) => (...args) => dispatch => {
  const action = createAction(name);

  dispatch({ type: `${name}_STARTED` });
  return dispatch(fun(...args))
    .then(
      payload => dispatch(action(payload)),
      error => dispatch(action(error))
    ));
};

const saveScore = createEffect(
  'SAVE_SCORE', 
  score => (_, __, {fetch}) => 
    fetch('/scores', { method: 'POST', { score } })
);

const mapDispatchToProps = ({ saveScore });

// snip connected test
import { expectRedux, storeSpy } from 'expect-redux';

it('dispatches a SAVE_SCORE after saving via dispatcher', () => {
  const fetch = createSpy().andReturn(Promise.resolve());
  const store = createStore(compose(storeSpy, thunk.withExtraArgument({fetch})));

  const connectedComponent = shallow(<Component store={store}/>);

  connectedComponent.props().saveScore(5);

  return expectRedux(store)
    .toDispatchAnAction()
    .matching({type: 'SAVE_SCORE'})
    .then(() => {
      expect(fetch).toHaveBeenCalledWith('/scores', { method: 'POST', { score: 5 }});
    });
});