使用Redux测试异步操作创建者并做出反应时，无法读取未定义的属性'.then' [英] Cannot read property '.then' of undefined when testing async action creators with redux and react

问题描述

我正在尝试使用react，redux-mock-store和redux编写一些测试，但是我一直在出错.也许是因为我的Promise尚未解决?

I'm trying to write some test using react, redux-mock-store and redux, but I keep getting and error. Maybe because my Promise has not yet been resolved?

fetchListing()动作创建者实际上可以在开发和生产中试用，但是在通过测试时遇到了问题.

The fetchListing() action creator actually works when I try it on dev and production, but I'm having problems making the test pass.

错误消息

(node:19143) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 3): SyntaxError
(node:19143) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
 FAIL  src/actions/__tests__/action.test.js
  ● async actions › creates "FETCH_LISTINGS" when fetching listing has been done

    TypeError: Cannot read property 'then' of undefined

      at Object.<anonymous> (src/actions/__tests__/action.test.js:44:51)
          at Promise (<anonymous>)
      at Promise.resolve.then.el (node_modules/p-map/index.js:42:16)
          at <anonymous>
      at process._tickCallback (internal/process/next_tick.js:169:7)

  async actions
    ✕ creates "FETCH_LISTINGS" when fetching listing has been done (10ms)

action/index.js

// actions/index.js
import axios from 'axios';

import { FETCH_LISTINGS } from './types';

export function fetchListings() {

  const request = axios.get('/5/index.cfm?event=stream:listings');

  return (dispatch) => {
    request.then(( { data } ) => {
      dispatch({ type: FETCH_LISTINGS, payload: data });
    });
  }
};

action.test.js

// actions/__test__/action.test.js

import configureMockStore from 'redux-mock-store';
import thunk from 'redux-thunk';
import { applyMiddleware } from 'redux';
import nock from 'nock';
import expect from 'expect';

import * as actions from '../index';
import * as types from '../types';


const middlewares = [ thunk ];
const mockStore = configureMockStore(middlewares);

describe('async actions', () => {
  afterEach(() => {
    nock.cleanAll()
})


it('creates "FETCH_LISTINGS" when fetching listing has been done', () => {
  nock('http://example.com/')
    .get('/listings')
    .reply(200, { body: { listings: [{ 'corpo_id': 5629, id: 1382796, name: 'masm' }] } })

    const expectedActions = [
      { type: types.FETCH_LISTINGS }, { body: { listings: [{ 'corpo_id': 5629, id: 1382796, name: 'masm' }] }}
    ]

    const store = mockStore({ listings: [] })

    return store.dispatch(actions.fetchListings()).then((data) => {
      expect(store.getActions()).toEqual(expectedActions)
    })
  })
})

推荐答案

store.dispatch(actions.fetchListings())返回undefined.您不能为此拨打.then.

store.dispatch(actions.fetchListings()) returns undefined. You can't call .then on that.

请参见 redux-thunk代码.它执行返回的函数并将其返回.您在fetchListings中返回的函数不返回任何内容，即undefined.

See redux-thunk code. It executes the function you return and returns that. The function you return in fetchListings returns nothing, i.e. undefined.

尝试

return (dispatch) => {
    return request.then( (data) => {
      dispatch({ type: FETCH_LISTINGS, payload: data });
    });
  }

之后，您仍然会遇到另一个问题.您不会在then内部返回任何内容，而只会进行分派.这意味着下一个then获取undefined参数

After that you will still have another problem. You don't return anything inside your then, you only dispatch. That means the next then gets undefined argument

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