The Complete Redux book

api.js

import 'whatwg-fetch';
import {API} from 'consts';
import {apiStarted, apiFinished, apiError} from 'actions/ui';

const apiMiddleware = ({dispatch}) => (next) => (action) => {
  if (action.type !== API) {
    return next(action);
  }

  const {url, success} = action.payload;

  dispatch(apiStarted());

  return fetch(url)
    .then((response) => response.json())
    .then((response) => {
      dispatch(apiFinished());
      dispatch(success(response));
    })
    .catch(({status, statusText}) => dispatch(apiError(new Error({status, statusText}))));
};

export default apiMiddleware;

thunk test.test.js

import apiMiddleware from 'middleware/api';
import {mockFetch, mockFetchError} from 'test-utils';
import {API_STARTED, API_FINISHED, API, API_ERROR} from 'consts';

const data = {title: 'hello'};

const setData = (data) => ({
  type: 'SET_DATA',
  payload: data,
});

const apiAction = () => ({
  type: API,
  payload: {
    success: setData,
    url: 'fake.json',
  },
});

describe('api middleware', () => {
  let next, dispatch, middleware;

  beforeEach(() => {
    next = jest.fn();
    dispatch = jest.fn();
    middleware = apiMiddleware({dispatch})(next);
  });

  describe('general', () => {
    // TODO
  });

  describe('success', () => {
    // TODO
  });

  describe('error', () => {
    // TODO
  });
});