如何在 React-Redux 中使用 Mocha、Chai 和 Enzyme 测试方法和回调

Question

我必须为PlayerList 容器和Player 组件编写单元测试用例。为分支和道具编写测试用例是可以的，但是我如何测试组件的方法和其中的逻辑。我的代码覆盖率不完整，因为方法没有经过测试。

场景：

父组件将对其方法onSelect 的引用作为回调传递给子组件。该方法在PlayerList 组件中定义，但Player 正在生成调用它的onClick 事件。

父组件/容器：

import React, { Component } from 'react';
import {connect} from 'react-redux';
import {bindActionCreators} from 'redux';
import {selectTab} from '../actions/index';
import Player from './Player';

class PlayerList extends Component {    
    constructor(props){
        super(props);
    }

    onSelect(i) {
        if (!i) {
            this.props.selectPlayer(1);
        }
        else {
            this.props.selectPlayer(i);
        }
    }

    createListItems(){      
        return this.props.playerList.map((item, i)=>{
            return (                
                    <Player key={i} tab={item} onSelect={() => this.onSelect(item.id)} />
                )
        });
    }

    render() {
        return(
            <div className="col-md-12">
                <ul className="nav nav-tabs">                   
                    {this.createListItems()}
                </ul>   
            </div>
        )   
    }   
}

function mapStateToProps(state){
  return {
    playerList: state.playerList 
  }
}
function matchDispatchToProps(dispatch){
  return bindActionCreators({selectPlayer: selectPlayer}, dispatch);
}
export default connect(mapStateToProps, matchDispatchToProps)(PlayerList);

子组件：

    import React, { Component } from 'react';
    class Player extends Component {    
        constructor(props){
            super(props);
        }

        render() {
            return(
                <li className={this.props.player.selected?'active':''}>
                    <a href="#"  onClick={() => this.props.onSelect(this.props.player.id)}>
                       <img src={this.props.player.imgUrl}     className="thumbnail"/>
                        {this.props.player.name}
                    </a>
                </li>
            )   
        }   
    }
    export default Player;

Answer 1

使用酶的.instance() 方法访问组件方法

当然有几个先决条件。

1. 您必须先渲染一次组件，使用酶的 shallow 或 mount 函数，具体取决于您是否需要 [和/或您喜欢的方式] simulate 嵌套事件孩子们。这也为您提供了一个酶包装器，您可以从中访问组件实例及其方法。
2. 您需要将sinon test spies 包裹在这些实例方法周围，并使用.update 重新渲染，以获得可以断言的带有间谍的包装器版本。

示例：

// Import requisite modules
import React from 'react';
import sinon from 'sinon';
import { mount } from 'enzyme';
import { expect } from 'chai';
import PlayerList from './PlayerList';

// Describe what you'll be testing
describe('PlayerList component', () => {
  // Mock player list
  const playerList = [
    {
      id    : 1,
      imgUrl: 'http://placehold.it/100?text=P1',
      name  : 'Player One'
    }
  ];

  // Nested describe just for our instance methods
  describe('Instance methods', () => {
    // Stub the selectPlayer method.
    const selectPlayer = sinon.stub();
    // Full DOM render including nested Player component
    const wrapper = mount(
      <PlayerList playerList={ playerList } selectPlayer={ selectPlayer } />
    );
    // Get the component instance
    const instance = wrapper.instance();

    // Wrap the instance methods with spies
    instance.createListItems = sinon.spy(instance.createListItems);
    instance.onSelect        = sinon.spy(instance.onSelect);

    // Re-render component. Now with spies!
    wrapper.update();

    it('should call createListItems on render', () => {
      expect(instance.createListItems).to.have.been.calledOnce;
    });

    it('should call onSelect on child link click', () => {
      expect(instance.onSelect).to.not.have.been.called;
      wrapper.find('li > a').at(0).simulate('click');
      expect(instance.onSelect).to.have.been.calledOnce;
      expect(instance.onSelect).to.have.been.calledWith(playerList[0].id);
    });
  });
});

注意事项：

• 当对PlayerList 和Player 使用上述代码时，我发现您没有将名为player 的道具分配给Player；相反，您分配的是item={ item }。为了让它在本地工作，我将其更改为 <Player player={ item } … />。
• 在onSelect 中，您正在检查接收到的i 参数是否为假，然后调用selectPlayer(1)。在上面的示例中，我没有为此包含测试用例，因为逻辑与我有关，原因有两个：
  1. 我想知道i 是否可以成为0？如果是这样，它将始终评估为错误并传递到该块中。
  2. 因为Player 调用onSelect(this.props.player.id)，我想知道this.props.player.id 是否会成为undefined？如果是这样，我想知道为什么您会在 props.playerList 中有一个没有 id 属性的项目。

但是如果你想测试现在的逻辑，它看起来像这样......

onSelect 中的示例测试逻辑：

describe('PlayerList component', () => {
  …
  // Mock player list should contain an item with `id: 0`
  // …and another item with no `id` property.
  const playerList = [
    …, // index 0 (Player 1)
    {  // index 1
      id    : 0,
      imgUrl: 'http://placehold.it/100?text=P0',
      name  : 'Player Zero'
    },
    {  // index 2
      imgUrl: 'http://placehold.it/100?text=P',
      name  : 'Player ?'
    }
  ];
  describe('Instance methods', { … });
  describe('selectPlayer', () => {
    const selectPlayer = sinon.stub();
    const wrapper = mount(
      <PlayerList playerList={ playerList } selectPlayer={ selectPlayer } />
    );
    const instance = wrapper.instance();

    // There is no need to simulate clicks or wrap spies on instance methods
    // …to test the call to selectPlayer. Just call the method directly.
    it('should call props.selectPlayer with `id` if `id` is truthy', () => {
      instance.onSelect(playerList[0].id); // id: 1
      expect(selectPlayer).to.have.been.calledOnce;
      expect(selectPlayer).to.have.been.calledWith(playerList[0].id);
    });

    it('should call props.selectPlayer(1) if `id` is 0', () => {
      instance.onSelect(playerList[1].id); // id: 0
      expect(selectPlayer).to.have.been.calledTwice;
      expect(selectPlayer).to.have.been.calledWith(1);
    });

    it('should call props.selectPlayer(1) if `id` is undefined', () => {
      instance.onSelect(playerList[2].id); // undefined
      expect(selectPlayer).to.have.been.calledThrice;
      expect(selectPlayer).to.have.been.calledWith(1);
    });
  });
});

Answer 2

您可以使用酶的simulate 函数来测试回调。您可以提供回调函数作为 sinon 的 spy 函数，并使用预期的参数验证它是否已被调用预期次数。 您可以在此处阅读更多信息： https://github.com/airbnb/enzyme/blob/master/docs/api/ShallowWrapper/simulate.md

这里是模拟回调函数的 Player 和 PlayerList 组件的单元测试。您需要单独的 PlayerList 组件作为 PlayerList 和 PlayerListContainer（表示该组件连接到 redux）。完成此操作后，您可以轻松地测试您的 PlayerList 组件。

PlayerListTest.jsx：

import React from 'react';
import { shallow } from 'enzyme';
import { expect } from 'chai';
import sinon from 'sinon';
import PlayerList from 'components/PlayerList';
import Player from 'components/Player';

describe('PlayerList test', () => {
  const playerList = [
    {
      id: '1',
      imgUrl: 'testimageurl',
      name: 'testplayer1'
    },
    {
      id: '23423',
      imgUrl: 'http://testimageurl2',
      name: 'testplayer2'
    },
    {
      id: '123124123',
      imgUrl: 'http://testimageurl23',
      name: 'testplayer142'
    }
  ];

  it('calls callback function with item id when player is selected', () => {
    const mockSelectPlayer = sinon.spy();
    const wrapper = shallow(<PlayerList playerList={playerList} selectPlayer={mockSelectPlayer} />);

    const playerWrapper = wrapper.find(Player);
    playerWrapper.at(0).simulate('select');

    expect(mockSelectPlayer.calledOnce).to.equal(true);
    expect(mockSelectPlayer.calledWith(playerList[0].id)).to.be.ok;
  });


});

PlayerTest.jsx：

import React from 'react';
import { shallow } from 'enzyme';
import { expect } from 'chai';
import sinon from 'sinon';
import Player from 'components/Player.jsx';

describe('Player test', () => {
  const player = {
    id: '1234',
    imgUrl: 'http://testimageurl',
    name: 'testplayer'
  };

  it('calls callback function when the .player-container element clicked', () => {
    const mockOnSelect = sinon.spy();
    const wrapper = shallow(<Player player={player} onSelect={mockOnSelect} />);

    wrapper.find('.player-container').simulate('click');

    expect(mockOnSelect.calledOnce).to.equal(true);
  });
});