React自动化测试(二)：环境搭建

[mwjuan]

安装

npm install --save-dev jest babel-jest enzyme enzyme-adapter-react-16
根据react版本安装对应的enzyme

配置

package.json

"scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
  - "test": "react-scripts test",
  + "test": "jest --",
    "eject": "react-scripts eject"
  }

• --coverage 参数可生成测试覆盖率报告
• --colors可根据覆盖率生成不同颜色的报告（<50%红色，50%~80%黄色， ≥80%绿色）

执行npx jest --init可自动生成配置文件，配置内容详解参考一文搞定前端自动化测试（React 实战）

jest.config.js

• roots 用于指定 Jest 的根目录，Jest 只会检测在根目录下的测试用例并运行
• setupFiles 用于指定创建测试环境前的准备文件，比如可执行的脚本、注册enzyme的兼容

/*
 * For a detailed explanation regarding each configuration property, visit:
 * https://jestjs.io/docs/configuration
 */

module.exports = {
  // All imported modules in your tests should be mocked automatically
  // automock: false,

  // Stop running tests after `n` failures
  // bail: 0,

  // The directory where Jest should store its cached dependency information
  // cacheDirectory: "/private/var/folders/74/c2mw_hms06zdrnx7v9bhqgzr0000gn/T/jest_dx",

  // Automatically clear mock calls, instances, contexts and results before every test
  clearMocks: true,

  // Indicates whether the coverage information should be collected while executing the test
  collectCoverage: true,

  // An array of glob patterns indicating a set of files for which coverage information should be collected
  // collectCoverageFrom: undefined,

  // The directory where Jest should output its coverage files
  coverageDirectory: "coverage",

  // An array of regexp pattern strings used to skip coverage collection
  coveragePathIgnorePatterns: [
    "/node_modules/"
  ],

  // Indicates which provider should be used to instrument code for coverage
  // coverageProvider: "babel",

  // A list of reporter names that Jest uses when writing coverage reports
  // coverageReporters: [
  //   "json",
  //   "text",
  //   "lcov",
  //   "clover"
  // ],

  // An object that configures minimum threshold enforcement for coverage results
  // coverageThreshold: undefined,

  // A path to a custom dependency extractor
  // dependencyExtractor: undefined,

  // Make calling deprecated APIs throw helpful error messages
  // errorOnDeprecated: false,

  // The default configuration for fake timers
  // fakeTimers: {
  //   "enableGlobally": false
  // },

  // Force coverage collection from ignored files using an array of glob patterns
  // forceCoverageMatch: [],

  // A path to a module which exports an async function that is triggered once before all test suites
  // globalSetup: undefined,

  // A path to a module which exports an async function that is triggered once after all test suites
  // globalTeardown: undefined,

  // A set of global variables that need to be available in all test environments
  // globals: {},

  // The maximum amount of workers used to run your tests. Can be specified as % or a number. E.g. maxWorkers: 10% will use 10% of your CPU amount + 1 as the maximum worker number. maxWorkers: 2 will use a maximum of 2 workers.
  // maxWorkers: "50%",

  // An array of directory names to be searched recursively up from the requiring module's location
  // moduleDirectories: [
  //   "node_modules"
  // ],

  // An array of file extensions your modules use
  // moduleFileExtensions: [
  //   "js",
  //   "mjs",
  //   "cjs",
  //   "jsx",
  //   "ts",
  //   "tsx",
  //   "json",
  //   "node"
  // ],

  // A map from regular expressions to module names or to arrays of module names that allow to stub out resources with a single module
  // moduleNameMapper: {},

  // An array of regexp pattern strings, matched against all module paths before considered 'visible' to the module loader
  // modulePathIgnorePatterns: [],

  // Activates notifications for test results
  // notify: false,

  // An enum that specifies notification mode. Requires { notify: true }
  // notifyMode: "failure-change",

  // A preset that is used as a base for Jest's configuration
  // preset: undefined,

  // Run tests from one or more projects
  // projects: undefined,

  // Use this configuration option to add custom reporters to Jest
  // reporters: undefined,

  // Automatically reset mock state before every test
  // resetMocks: false,

  // Reset the module registry before running each individual test
  // resetModules: false,

  // A path to a custom resolver
  // resolver: undefined,

  // Automatically restore mock state and implementation before every test
  // restoreMocks: false,

  // The root directory that Jest should scan for tests and modules within
  // rootDir: undefined,

  // A list of paths to directories that Jest should use to search for files in
  roots: ['<rootDir>/src/'],
  modulePaths:['<rootDir>'],

  // Allows you to use a custom runner instead of Jest's default test runner
  // runner: "jest-runner",

  // The paths to modules that run some code to configure or set up the testing environment before each test
  setupFiles: ['<rootDir>/jest.setup.js'], 

  // A list of paths to modules that run some code to configure or set up the testing framework before each test
  // setupFilesAfterEnv: [],

  // The number of seconds after which a test is considered as slow and reported as such in the results.
  // slowTestThreshold: 5,

  // A list of paths to snapshot serializer modules Jest should use for snapshot testing
  // snapshotSerializers: [],

  // The test environment that will be used for testing
  testEnvironment: "jsdom",

  // Options that will be passed to the testEnvironment
  // testEnvironmentOptions: {},

  // Adds a location field to test results
  // testLocationInResults: false,

  // The glob patterns Jest uses to detect test files
  // testMatch: [
  //   "**/__tests__/**/*.[jt]s?(x)",
  //   "**/?(*.)+(spec|test).[tj]s?(x)"
  // ],

  // An array of regexp pattern strings that are matched against all test paths, matched tests are skipped
  testPathIgnorePatterns: [
    "/node_modules/"
  ],

  // The regexp pattern or array of patterns that Jest uses to detect test files
  // testRegex: [],

  // This option allows the use of a custom results processor
  // testResultsProcessor: undefined,

  // This option allows use of a custom test runner
  // testRunner: "jest-circus/runner",

  // A map from regular expressions to paths to transformers
  // transform: undefined,

  // An array of regexp pattern strings that are matched against all source file paths, matched files will skip transformation
  transformIgnorePatterns: [
    "/node_modules/",
    // "\\.pnp\\.[^\\/]+$"
  ],

  // An array of regexp pattern strings that are matched against all modules before the module loader will automatically return a mock for them
  // unmockedModulePathPatterns: undefined,

  // Indicates whether each individual test should be reported during the run
  // verbose: undefined,

  // An array of regexp patterns that are matched against all source file paths before re-running tests in watch mode
  // watchPathIgnorePatterns: [],

  // Whether to use watchman for file crawling
  watchman: true
};

jest.setup.js

import { configure } from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';

// 注册enzyme版本兼容
configure({ adapter: new Adapter() });

Object.defineProperty(window, 'matchMedia', {
    writable: true,
    value: jest.fn().mockImplementation(query => ({
        matches: false,
        media: query,
        onchange: null,
        addListener: jest.fn(), // Deprecated
        removeListener: jest.fn(), // Deprecated
        addEventListener: jest.fn(),
        removeEventListener: jest.fn(),
        dispatchEvent: jest.fn(),
    })),
});

测试示例(下节详解)

import React from 'react';
import { mount } from 'enzyme';
import Example from './Example'
import { act } from 'react-dom/test-utils';

describe('Enzyme shallow', function () {
    let value;
    let app;

    beforeAll(async () => {
        value = '按钮内容';
        await act(async () => {
            app = mount(<Example value={value} />)
            app.debug();
        })
    })

    afterAll(() => {
        value = null;
        app.unmount();
    })

    // 根据标签找dom节点   
    it('1. button by tag', async () => {
        let button = app.find('button');
        expect(button.get(0).props.children[1][0].props.children).toBe(value);
    })

    // 根据className找dom节点   ||   根据id找find('#not')
    it('2. button by className', async () => {
        let button = app.find('.test-button')
        expect(button.get(0).props.children).toBe(value);
    })

    // 测试button点击事件
    it('3. button onClick', async () => {
        let button = app.find('.test-button');
        button.at(0).simulate('click');
        expect(app.state('text')).toBe(`click-${value}`);

        let button1 = app.find('.name');
        button1.at(0).simulate('click');
        button = app.find('.test-button');
        app.update();
        expect(button.get(0).props.children).toBe(value);
    })

    // get input value
    it('4. input value', async () => {
        let input = app.find('.input');
        expect(input.get(0).props.value).toBe(value);
    })

    // 测试Input onChange事件
    it('5. input onchange', async () => {
        let input = app.find('.input');
        input.at(0).simulate('change', { target: { value: 6616 } });
        app.update();
        input = app.find('.input');
        expect(input.get(0).props.value).toBe('click-6616')
    })

    // 测试生命周期
    it('6. life cycle', async () => {
        const appInstance = app.instance();
        expect(appInstance).toBeInstanceOf(Example);
        appInstance.componentDidMount();
        expect(app.state('value')).toBe(777); // 判断state值变化
    })

    // 测试方法调用
    it('7. function', async () => {
        let ins = app.instance();
        let spy = jest.spyOn(ins, 'save');
        ins.save();
        app.update()
        ins.forceUpdate()
        expect(spy).toBeCalledTimes(1)
    })
})

测试报告

• % stmts是语句覆盖率（statement coverage）：每个语句是否都执行了
• % Branch分支覆盖率（branch coverage）：条件语句是否都执行了
• % Funcs函数覆盖率（function coverage）：函数是否全都调用了
• % Lines行覆盖率（line coverage）：未执行的代码行数

参考：

1. enzyme
2. Jest
3. window.matchMedia不是一个函数的解决方法