Redux-Loop Reducer boilerplate

reducer.js

/// @ts-check

import { loop, Cmd } from 'redux-loop';
import { error } from 'lib/result';

import { fetchItem } from 'effects/itemEffects';
import { ITEM_LOCATION } from 'constants/routerConstants';

const initState = {
  fetching: null,
  data: error()
};

const ITEM_RECEIVED_SUCCESS = 'ITEM_RECEIVED_SUCCESS';
const ITEM_RECEIVED_ERROR = 'ITEM_RECEIVED_ERROR';

export const fetchItemSuccess = () => ({ type: ITEM_RECEIVED_SUCCESS });
export const fetchItemError = () => ({ type: ITEM_RECEIVED_ERROR });

const createFetchLoop = (state, _action) =>
  loop(
    { ...state, fetching: true },
    Cmd.run(fetchItem, {
      successActionCreator: fetchItemSuccess,
      failActionCreator: fetchItemError
    })
  );

export function itemReducer(state = initState, action = {}) {
  switch (action.type) {
    case ITEM_LOCATION: {
      return createFetchLoop(state, action);
    }

    case ITEM_RECEIVED_SUCCESS: {
      console.log(ITEM_RECEIVED_SUCCESS);
      return state;
    }

    default:
      return state;
  }
}

test.js

/// @ts-check

import { loop, Cmd } from 'redux-loop';
import assert from 'assert';
import { error } from 'lib/result';

import { ITEM_LOCATION } from 'constants/routerConstants';
import { fetchItem } from 'effects/itemEffects';

import { itemReducer, fetchItemSuccess, fetchItemError } from './itemReducer';

const createState = ({ fetching = null, data = error() } = {}) => ({
  fetching,
  data
});

describe('itemReducer', () => {
  it('Init state', () => {
    const actual = itemReducer();
    const expected = createState();

    assert.deepEqual(actual, expected);
  });

  it('ITEM_LOCATION', () => {
    const actual = itemReducer(undefined, { type: ITEM_LOCATION });
    const expected = loop(
      createState({ fetching: true }),
      Cmd.run(fetchItem, {
        successActionCreator: fetchItemSuccess,
        failActionCreator: fetchItemError
      })
    );

    assert.deepEqual(actual, expected);
  });
});