reactjs - 如何在 React 组件中对这些三元表达式实现 100% 的测试覆盖率

Question

我正在尝试学习测试驱动开发，所以我创建了一个简单的培训应用程序，它由 2 个简单的工作组件 App.js 组成，它将来自虚拟本地 JSON 文件的数据数组保存到 App.js 组件state 然后通过它映射并渲染一个 User 组件，其中包含数据数组的每个元素的 props。所以我有 3 条未覆盖的行，它们都包含“if 语句”，我想对它们实现 100% 的测试覆盖率，所以请帮忙。以下是测试结果。

这些是 App.js 的第 18 行和第 32 行中未覆盖的行是每个函数中的三元表达式

clickFollowHandler(id) {
    this.setState(prevState => {
        const updatedUsers = prevState.users.map(user => {
            if (user.id === id) {
              user.isFollowed === 'active' ? user.isFollowed = 'idle' : user.isFollowed = 'active'
            }
            return user
        })
        return {
            users: updatedUsers
        }
    })
  }

clickStarHandler(id) {
    this.setState(prevState => {
        const updatedUsers = prevState.users.map(user => {
            if (user.id === id) {
              user.isStared === 'active' ? user.isStared = 'idle' : user.isStared = 'active'
            }
            return user
        })
        return {
            users: updatedUsers
        }
    })
  }

这是 User.js 的第 23 行是复选框的三元表达式

return(
      <div className={classes.container} key={id}>
        <img className={classes.imageContainer} src={myImage} alt={name} />
        <div className={classes.contentContainer}>
          <div className={classes.contentContainerRow1}>
            <div className={classes.name}>name: {name}</div>
            <button onClick={() => handleFollowClick(id)}>
              {isFollowed === 'active' ? 'Unfollow' : 'Follow'}
            </button>
          </div>
          <div className={classes.contentContainerRow2}>
            <div className={classes.date}>date: {date}</div>
            <div className={classes.time}>reading time: {readingTime}</div>
            <input 
              className={classes.hvrIconPop}
              checked={isStared === 'active' ? true : false} 
              onChange={() => handleStarClick(id)}
              type='checkbox' 
            />
          </div>
        </div>
      </div>
    )

现在这是我的 App.test.js

import React from 'react';
import ReactDOM from 'react-dom';
import {shallow, mount} from './enzyme';
import App from './App';

jest.mock('./data/users-data.json')
let {user} = require('./data/users-data.json')


describe('App Component', () => {
  it('calling the clickFollowHandler method from App Component has the expected effect on the state of the first user', () => {
    const AppComponent = shallow(<App />)
    const wrapper = AppComponent.instance()
    wrapper.clickFollowHandler('5d552d0058f193f2795fc814')
    expect(wrapper.state.users[0].isFollowed).toMatch('idle')
  })
})




describe('App Component', () => {
  it('calling the clickStarHandler method from App Component has the expected effect on the state of the second user', () => {
    const AppComponent = shallow(<App />)
    const wrapper = AppComponent.instance()
    wrapper.clickStarHandler('5d552d00b20b141dff10d2a2')
    expect(wrapper.state.users[1].isStared).toEqual('idle')
  })
})

和我的 User.test.js

import React from 'react';
import renderer from 'react-test-renderer';
import {shallow, mount} from '../../enzyme';

import User from './User';

const users = {
  "id": "5d552d0058f193f2795fc814",
  "isFollowed": "active",
  "isStared": "idle",
  "image": "./assets/images/avata.png",
  "readingTime": 20,
  "name": "Walton Morton",
  "date": "Aug 9"
};

it('renders correctly when there are no users', () => {
  const tree = renderer.create(<User 
    key={''}
    id={''}
    name={''}
    date={''}
    readingTime={''}
    isStared={''}
    isFollowed={''}
    image={''}
    handleFollowClick={() => {}}
    handleStarClick={() => {}} 
  />).toJSON();
  expect(tree).toMatchSnapshot();
});

it('renders correctly when there is one user', () => {

  const tree = renderer.create(<User 
    key={users.id}
    id={users.id}
    name={users.name}
    date={users.date}
    readingTime={users.readingTime}
    isStared={users.isStared}
    isFollowed={users.isFollowed}
    image={users.image}
    handleFollowClick={() => 'test'}
    handleStarClick={() => {}}
  />).toJSON();
  expect(tree).toMatchSnapshot();
});




it('when the follow button is clicked a callback is executed', () => {
  const mockFollowClick = jest.fn();
  const mockStarClick = jest.fn();

  const tree = renderer.create(<User 
    key={users.id}
    id={users.id}
    name={users.name}
    date={users.date}
    readingTime={users.readingTime}
    isStared={users.isStared}
    isFollowed={users.isFollowed}
    image={users.image}
    handleFollowClick={mockFollowClick}
    handleStarClick={mockStarClick}
  />)

  const button = tree.root.findByType('button');
  const input = tree.root.findByType('input');

  button.props.onClick();
  expect(mockFollowClick).toHaveBeenCalled();

  button.props.onClick();
  expect(mockFollowClick).toHaveBeenCalledWith('5d552d0058f193f2795fc814');

  input.props.onChange();
  expect(mockStarClick).toHaveBeenCalled();
})





describe('User Component', () => {
  it('clicking on the button will trigger the click handler', () => {
    const mockFollowHandler = jest.fn();
    const mockStarHandler = jest.fn();
    const wrapper = mount(<User 
      key={users.id}
      id={users.id}
      name={users.name}
      date={users.date}
      readingTime={users.readingTime}
      isStared={users.isStared}
      isFollowed={users.isFollowed}
      image={users.image}
      handleFollowClick={mockFollowHandler} 
      handleStarClick={mockStarHandler} 
    />)
    wrapper.find('button').simulate('click');
    expect(mockFollowHandler).toHaveBeenCalledWith('5d552d0058f193f2795fc814')
  })

  it('changing the star checkbox will trigger an onChange handler', () => {
    const mockFollowHandler = jest.fn();
    const mockStarHandler = jest.fn();
    const wrapper = mount(<User 
      key={users.id}
      id={users.id}
      name={users.name}
      date={users.date}
      readingTime={users.readingTime}
      isStared={users.isStared}
      isFollowed={users.isFollowed}
      image={users.image}
      handleFollowClick={mockFollowHandler} 
      handleStarClick={mockStarHandler} 
    />)
    wrapper.find('input').simulate('change');
    expect(mockStarHandler).toHaveBeenCalledWith('5d552d0058f193f2795fc814');
  })
});

Answer 1

您需要针对三元表达式的两个条件(而不仅仅是一个)进行测试。由于我看不到完整的代码，我将尝试提供一些简短的注释:

对于 clickStarHandler 和 clickFollowHandler，您需要针对 users 状态进行测试并手动调用类字段(正如您所做的那样).但是，当 isFollowed/isStarred 匹配 active 和匹配 idle 时，您需要满足条件.相当简单的过程，但是，如果您需要更新 users 状态以包含一些数据，那么您可以简单地使用 wrapper.setState({ users: userData }); .

用于测试应用:

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

// for simplicity, I'd recommend only using one user
const usersData = [
  {
    id: "5d552d0058f193f2795fc814",
    isFollowed: "active",
    isStarred: "idle",
    image: "./assets/images/avatar.png",
    readingTime: 20,
    name: "Walton Morton",
    date: "Aug 9"
  }
];

// *optional* include any props that are needed for the App 
const initialProps = {};

describe("App Component", () => {
  let wrapper;
  beforeEach(() => (
    wrapper = mount(<App { ...initialProps }/>);
    wrapper.setState({ users: usersData }); // not needed if user data is already defined in state
  )}

  it("sets the 'user.isStarred' state to 'active' or 'idle'", () => (
    const invokeStarHandler = () => {
      wrapper.instance().clickStarHandler("5d552d0058f193f2795fc814");
      wrapper.update();
    };

    invokeStarHandler();

    expect(wrapper.state("users[0].isStarred").toEqual("active");

    invokeStarHandler();

    expect(wrapper.state("users[0].isStarred").toEqual("idle");
  });

  it("sets the 'user.isFollowed' state to 'active' or 'idle'", () => (
    const invokeFollowHandler = () => {
      wrapper.instance().clickFollowHandler("5d552d0058f193f2795fc814");
      wrapper.update();
    };

    invokeFollowHandler();

    expect(wrapper.state("users[0].isFollowed").toEqual("idle");

    invokeFollowHandler();

    expect(wrapper.state("users[0].isFollowed").toEqual("active");
  });

  ...etc.
});

对于 Users 测试，只需操作用户属性；例如，更改 wrapper.setProps({ isStarred: "active"}) 或 wrapper.setProps({ isStarred: "idle"})，然后搜索 输入并根据其属性进行测试:

import React from 'react";
import { mount } from "enzyme";
import Users from "../Users";

// include any props that are needed for the Users component 
const initialProps = {
  id: "5d552d0058f193f2795fc814",
  isFollowed: "active",
  isStarred: "idle",
  image: "./assets/images/avatar.png",
  readingTime: 20,
  name: "Walton Morton",
  date: "Aug 9"
}

describe("Users Component", () => {
  let wrapper;
  beforeEach(() => (
    wrapper = mount(<Users { ...initialProps }/>);
  )}

  it("updates the input's 'checked' property based upon a 'isStarred' prop", () => (    
   expect(wrapper.find("input").props().checked).toBeFalsy();

   wrapper.setProps({ isStarred: "active" });

   expect(wrapper.find("input").props().checked).toBeTruthy();
  });

  ...etc
});

---

附带说明，您可以使用 object destructuring和 spread syntax大大简化您的 React 组件代码。