ComponentDidMount() 中 Axios 请求的 Jest/酶单元测试

IT技术 reactjs jestjs enzyme
2021-05-19 00:49:37

我正在尝试使用 Jest 和 Enzyme 对我现有的 React 应用程序执行一些单元测试。我对这些东西完全陌生，准确地说我不知道​​如何处理这样的测试场景。我知道要测试 API 请求调用，我必须执行一些“模拟”，但是我应该如何为此编写测试？需要遵循哪些步骤？

以下是我要测试的代码片段。

主页.js

import React,{Component} from 'react'
import axios from 'axios';
import {Link} from 'react-router-dom';
import FacilityModal from '../Table/FacilityModal';

class Home extends Component {
  state = {
    cities:[],
    name:''
  }
 
  componentDidMount() {
    axios.get('/cities').then(res => {
      this.setState({cities:res.data})
      console.log("Oza" + JSON.stringify(res))
    });
    console.log(this.state.cities)
  }
 
  render() {
    let postList = this.state.cities.map(city => {
      return(
        <div key = {city.id}>
          <p>
            <Link to = {'/'+city.id}>{city.name}</Link>
          </p>
        </div>
      )
    })
    return(
      <div className = 'align'>All Facilities (NCAL)
        <div className="hr-sect">OR</div>
        <div className = 'Modal'>
          {postList}
        </div>
        <FacilityModal cityname = {this.props} />
      </div>
    )
  }
}
2个回答

import React from 'react';
import axios from 'axios';

export default class ArticleList extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      articles: []
    }
  }

  componentDidMount() {
    return axios.get('GET_ARTICLES_URL').then(response => {
      this.setState({
        articles: response.data
      });
    });
  }

  render() {
    return (
      <ul>
        {this.state.articles.map(a => <li><a href={a.url}>{a.title}</a></li>)}
      </ul>
    )
  }
}

// ---------

import React from 'react';
import { shallow } from 'enzyme';
import App from './App';

jest.mock('axios', () => {
  const exampleArticles = [
    { title: 'test article', url: 'test url' }
  ];
  
  return {
    get: jest.fn(() => Promise.resolve(exampleArticles)),
  };
});

const axios = require('axios');

it('fetch articles on #componentDidMount', () => {
  const app = shallow(<App />);
  app
    .instance()
    .componentDidMount()
    .then(() => {
      expect(axios.get).toHaveBeenCalled();
      expect(axios.get).toHaveBeenCalledWith('articles_url');
      expect(app.state()).toHaveProperty('articles', [
        { title: 'test article', url: 'test url' }
      ]);
      done();
    });
});

1) 在另一个返回Promise的方法中提取 API 调用（例如：fetchCities()）以便于测试。

2) 用 Jest 模拟 axios 节点module。参考文档：https : //jestjs.io/docs/en/mock-functions#mocking-modules

3) 使用 Enzyme 获取对您的组件的引用：https : //airbnb.io/enzyme/docs/api/ShallowWrapper/shallow.html

一旦到位，您可以验证状态是否设置正确。例如：

test('should fetch users', () => {
  const wrapper = shallow(<Home/>);
  const resp = {data: [{cities: ['NY']}]};

  axios.get.mockResolvedValue(resp);

  wrapper.instance().fetchCities().then(resp => {
     expect(wrapper.state('cities')).toEqual(resp.data.cities);
  });

});

我如何改进这个答案？这不是我所期待的城市名称的回应。

axios.js（promise 的单独函数）

'use strict';
module.exports = {
  get: () => {
    return Promise.resolve({
      data: [
        {
          id: 0,
          name: 'Santa Clara'
        },
        {
          id: 1,
          name: 'Fremont'
        }
      ]
    });
  }
};

Home.test.js（实际测试文件）

import React from 'react';
import { shallow,configure } from 'enzyme';
import Home from './Home';
import axios from 'axios';
import Adapter from 'enzyme-adapter-react-16';

configure({adapter:new Adapter()});

jest.mock('axios');


describe('Home component', () => {
  describe('when rendered', () => {
    it('should fetch a list of cities', () => {
      const getSpy = jest.spyOn(axios, 'get');
      const cityInstance = shallow(
        <Home/>
      );
      expect(getSpy).toBeCalled();
    });
  });
});
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