Question

有人用jsdom或类似的玩笑来测试自定义元素的设置很好吗？我一直在使用Puppeteer ans Selenium，但是它们会减慢测试速度。是否有其他替代品或对jsdom的修复可以使以下测试可运行？

import {LitElement} from 'lit-element';
import {html} from 'lit-html';

export class Counter extends LitElement {
  static get properties() {
    return Object.assign({}, super.properties, {
      count: {type: Number}
    });
  }

  render() {
    return html`Count is ${this.count}`;
  }
}

customElements.define('c-counter', Counter);

带有测试文件：

import './counter';

describe('c-counter', () => {
  it('should be registered', () => {
    expect(customElements.get('c-counter')).toBeDefined();
  });

  it('render', async () => {
    const element = window.document.createElement('c-counter');
    window.document.body.appendChild(element);

    await element.updateComplete;
    expect(element.innerHTML).toContain('Count is undefined');

    element.count = 3;
    await element.updateComplete;

    expect(element.innerHTML).toContain('Count is 3');
  });
});

最后这是当前的笑话环境设置：

const {installCommonGlobals} = require('jest-util');
const {JSDOM, VirtualConsole} = require('jsdom');
const JSDOMEnvironment = require('jest-environment-jsdom');
const installCE = require('document-register-element/pony');

class JSDOMCustomElementsEnvironment extends JSDOMEnvironment {
  constructor(config, context) {
    super(config, context);

    this.dom = new JSDOM('<!DOCTYPE html>', {
      runScripts: 'dangerously',
      pretendToBeVisual: true,
      VirtualConsole: new VirtualConsole().sendTo(context.console || console),
      url: 'http://jsdom'
    });

    /* eslint-disable no-multi-assign */
    const global = (this.global = this.dom.window.document.defaultView);

    installCommonGlobals(global, config.globals);

    installCE(global.window, {
      type: 'force',
      noBuiltIn: false
    });
  }

  teardown() {
    this.global = null;
    this.dom = null;

    return Promise.resolve();
  }
}

module.exports = JSDOMCustomElementsEnvironment;

Answer 1

可以通过一些其他设置来实现。

如果您查看开放的wc文档，他们建议在已经使用Karma和Headless Chrome进行浏览器中测试Web组件。正如您已经指出的，Puppeteer和Selenium对此太慢了，唯一可行的浏览器替代品是ElectronJS。 Jest有一个跑步者。

https://github.com/hustcc/jest-electron

这将使您能够在具有访问Shadow DOM权限的真实浏览器中呈现Web组件，并且测试仍将很快。像这样，我使用Webpack来处理我的代码。

// button.ts
import {html, customElement, LitElement, property} from "lit-element";

@customElement('awesome-button')
export class Button extends LitElement {

    @property()
    buttonText = '';

    render() {
        return html`<button id="custom-button"
            @click="${() => {}}">${this.buttonText}</button>`;
    }
}

Webpack配置

const path = require('path');
const {CleanWebpackPlugin} = require('clean-webpack-plugin');

module.exports = {
    mode: 'development',
    entry: './index.ts',
    module: {
        rules: [
            {
                test: /\.ts?$/,
                use: 'ts-loader',
                exclude: /node_modules/,
            },
        ],
    },
    resolve: {
        extensions: ['.tsx', '.ts', '.js'],
    },
    plugins: [
        new CleanWebpackPlugin()
    ],
    output: {
        filename: 'main.js',
        path: path.resolve(__dirname, 'dist'),
    },
};

最好的配置

module.exports = {
    preset: 'ts-jest',
    runner: 'jest-electron/runner',
    testEnvironment: 'jest-electron/environment',
    setupFiles: ['./dist/main.js'],
};

最后是我们的测试。

import {LitElement} from 'lit-element';

describe('awesome-button', () => {

    const AWESOME_BUTTON_TAG = 'awesome-button';
    const ELEMENT_ID = 'custom-button';
    let buttonElement: LitElement;

    const getShadowRoot = (tagName: string): ShadowRoot => {
        return document.body.getElementsByTagName(tagName)[0].shadowRoot;
    }

    beforeEach(() => {
        buttonElement = window.document.createElement(AWESOME_BUTTON_TAG) as LitElement;
        document.body.appendChild(buttonElement);
    });

    afterEach(() => {
       document.body.getElementsByTagName(AWESOME_BUTTON_TAG)[0].remove();
    });

    it('displays button text', async () => {
        const dummyText = 'Web components & Jest with Electron';
        buttonElement.setAttribute('buttonText', dummyText);
        await buttonElement.updateComplete;

        const renderedText = getShadowRoot(AWESOME_BUTTON_TAG).getElementById(ELEMENT_ID).innerText;

        expect(renderedText).toEqual(dummyText);
    });
    it('handles clicks', async () => {
        const mockClickFunction = jest.fn();
        buttonElement.addEventListener('click', () => {mockClickFunction()});

        getShadowRoot(AWESOME_BUTTON_TAG).getElementById(ELEMENT_ID).click();
        getShadowRoot(AWESOME_BUTTON_TAG).getElementById(ELEMENT_ID).click();

        expect(mockClickFunction).toHaveBeenCalledTimes(2);
    });
});

我什至写了一篇关于此的博客文章，在那里您可以找到具有完整设置等的存储库。

https://www.ninkovic.dev/blog/2020/testing-web-components-with-jest-and-lit-element

如何通过玩笑来测试Web组件（照明元件）

1 个答案: