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JavaScript Testing Notes

Testing Pyramid​

  • Unit testing.
  • Module testing.
  • Integration testing.
  • System testing.
  • E2E testing.

Testing Model​

PIE Model​

  • (Execution) Fault.
  • (Infection) Error.
  • (Propagation) Failure.

Heuristic Test Strategy Model​

软件功能测试 (难以实现完全自动化):

  • 关注价值(Value)：用户得到价值
  • 风险驱动(Risk)：降低价值/用户体验的风险项
  • 产品元素(Product Elements)
  • 结构(Structure):产品物理元素(如代码、硬件、配置文件)
  • 功能(Function):产品功能
  • 数据(Data):产品所操作的数据(如输入、输出)
  • 接口(Interface):产品所使用/暴露出的接口
  • 平台(Platform):产品所依赖的外部元素(如操作系统、输入/输出设备)
  • 操作(Operation):产品被使用的方式(如键盘、鼠标、触摸等命令操作)
  • 时间(Time):影响产品的时间因素
  • 组合元素:测试产品功能间协作

User Experience Testing​

对软件功能测试的有益补充:

  • 功能性体验
  • 易用性体验
  • 性能体验
  • 可靠性体验(如软件兼容性)

Mobile Testing​

  • 机型碎片化.
  • 屏幕碎片化.
  • 环境碎片化.
  • 耗电量.

Testing Design​

FAIR Principle​

  • Fast tests: break down into small separate and well structured tests.
  • Automated tests.
  • Isolated tests: any particular test should not depend on any others.
  • Repeatable tests: mock everything you can't control:
    • 3rd-party libraries.
    • 3rd-party APIs.
    • Timer API: jest.useFakerTimers()/jest.advanceTimersByTime()/cy.clock().
    • Date API: jest.spyOn(Date.prototype)/cy.tick().
    • Math.random() API: jest.spyOn()/jest.mock()/cy.stub().
  • 如果不能保持测试套件的确定性和速度, 那么它将成为生产力的障碍.

AAA Pattern​

Structure every test to 3 part code:

  • Arrange.
  • Act.
  • Assert.

Test-Driven Development​

Test-Driven Development Upside​

  • Reduce costs: find bugs early.
  • Reduce fear and anxiety.
  • Lead to better-designed and more testable code.
  • Make tests more thorough (彻底的). Easy to refactor legacy code.

Test-Driven Development Use Case​

  • Pure function.
    • 工具函数.
    • 数据转换函数.
    • 后端接口函数.
  • Bug fix:
    • Add failed testing first.
    • One bug fixed, one or more testing added.
  • UI interaction.

测试路径​

起始顶点至终止顶点.

Testing Methods​

Basic Testing Types​

  • Positive tests: valid inputs, verify functions.
  • Negative tests: invalid inputs (e.g null/undefined/''/mismatch type/mismatch structure) verify robustness.
  • Exception tests: expect(api()).toThrow(error).
  • Bottom-up testing: gives more granular feedback but slows down iteration speed.
  • Top-down testing: allows to iterate more quickly but will generate more coarse feedback.

图结构覆盖方法​

  • 顶点覆盖,边覆盖,边对覆盖(三顶点,两邻边)
  • VC/EC/EPC 法

数据流覆盖方法​

  • 数据流覆盖:定义处覆盖,使用处覆盖
  • DU 法(Data&Use)

逻辑覆盖方法​

  • 逻辑覆盖:条件处覆盖,判定处覆盖
  • DC(Decision),CC(Condition)法
  • MC/DC 法
  • MCC 法(完全覆盖)

随机测试方法​

  • ART(随机测试):每个用例间"距离"尽可能远

黑盒测试方法​

  • 等价类划分:合法输入(软件功能),非法输入(异常处理)
  • 等价类的边界值分析:合法 MIN,MIN+,MAX-,MAX 非法:MIN-,MAX+
  • 决策表+组合测试:简化决策表(考虑输入相关性)
    • 组合用例:维度与测试准度成正比
    • 约束用例:需避开约束输入(输入相关性,同时输入会成为无效输入)
    • 测试用例约简+测试用例优先级:额外贪心算法进行化简+排序测试用例求得近似解

Fault Location​

  • 代码可疑度= (失败测试用例经过数/失败测试用例总数)/ (成功测试用例经过数/成功测试用例总数+失败测试用例经过数/失败测试用例总数)

即在执行过目标代码的测试用例中失败测试用例占比

Fuzzing Testing​

Fuzzing 是一种通过向目标系统提供非预期的输入并监视异常结果来发现软件漏洞的方法.

Testable Code​

  • 完整注释.
  • 最小复杂度 = (扇入 * 扇出) ^ 2.
  • 可隔离性: 最小依赖性 + 松耦合性.
  • 使用依赖注入, 将外部对象移至函数参数处(不在函数内部调用构造器): 易于构造 mock/stub, 降低扇出(函数复杂度).

圈复杂度​

V(G) = e - n + 2: **<10**.

函数复杂度​

函数复杂度 = (扇入 * 扇出) ^ 2.

扇出​

引用:

  • 所引用外部对象/方法之和.
  • 扇出: **<7**.
  • 高扇出: 高复杂度/高依赖性/高耦合度.

扇入​

被引用:

  • 其他对象/方法引用此函数的次数之和.
  • 低扇入: 顶层代码, 不常用模块.
  • 高扇入: 标准库与工具类, 高扇入模块需要保持稳定.

耦合度​

内容耦合​

5 级耦合度:

O.property = 'tazimi'
O.method = function () {}
O.prototype.method = function () {}

公共耦合​

4 级耦合度, 共享全局变量:

let Global = 'global'

function A() {
  Global = 'A'
}
function B() {
  Global = 'B'
}

控制耦合​

3 级耦合度:

const absFactory = new AbstractFactory({ env: 'TEST' })

印记耦合​

2 级耦合度:

O.prototype.makeBread = function (args) {
  return new Bread(args.type, args.size)
}

O.makeBread({ type: wheat, size: 99, name: 'foo' })

数据耦合​

1 级耦合度.

无耦合​

0 级耦合度.

Unit Testing​

Unit Testing Principles​

  • 代码覆盖率.
  • 非法值测试.
  • 边界测试.
  • 非边界测试.

Testing Code Isolation​

  • 编写代码时, 保持最小复杂度(最小依赖, 最低耦合).
  • 利用 mock/stub 模拟外部依赖/测试数据.

Testing Mocks​

  • mock: 模拟对象中的方法/接口
  • stub: 模拟对象中的返回值
  • spy: 在原有对象的基础上, 增加监视用变量/方法 e.g assert/调用次数/参数限制
const mockery = require('mockery')
mockery.enable()

describe('Sum suite File', () => {
  beforeEach(() => {
    mockery.registerAllowable('./mySumFS', true)
  })

  afterEach(() => {
    mockery.deregisterAllowable('./mySumFS')
  })

  it('Adds Integers!', () => {
    const filename = 'numbers'
    const fsMock = {
      readFileSync(path, encoding) {
        expect(path).toEqual(filename)
        expect(encoding).toEqual('utf8')
        return JSON.stringify({ a: 9, b: 3 })
      },
    }

    mockery.registerMock('fs', fsMock)
    const mySum = require('./mySumFS')
    expect(mySum.sum(filename)).toEqual(12)
    mockery.deregisterMock('fs')
  })
})

Headless Testing​

const puppeteer = require('puppeteer')

;(async () => {
  const browser = await puppeteer.launch()
  const page = await browser.newPage()
  await page.goto('https://example.com')
  await page.screenshot({ path: 'example.png' })
  await browser.close()
})()

Browser Context​

// Create a new incognito browser context
const context = await browser.createIncognitoBrowserContext()
// Create a new page inside context.
const page = await context.newPage()
// ... do stuff with page ...
await page.goto('https://example.com')
// Dispose context once it's no longer needed.
await context.close()

DOM Testing​

page.$(selector) same to querySelector

Event Testing​

// wait for selector
await page.waitFor('.foo')
// wait for 1 second
await page.waitFor(1000)
// wait for predicate
await page.waitFor(() => !!document.querySelector('.foo'))
const puppeteer = require('puppeteer')

puppeteer.launch().then(async (browser) => {
  const page = await browser.newPage()
  const watchDog = page.waitForFunction('window.innerWidth < 100')
  await page.setViewport({ width: 50, height: 50 })
  await watchDog
  await browser.close()
})
const [response] = await Promise.all([
  page.waitForNavigation(), // The promise resolves after navigation has finished
  page.click('a.my-link'), // Clicking the link will indirectly cause a navigation
])
const firstRequest = await page.waitForRequest('http://example.com/resource')
const finalRequest = await page.waitForRequest(
  request =>
    request.url() === 'http://example.com' && request.method() === 'GET'
)
return firstRequest.url()
const firstResponse = await page.waitForResponse('https://example.com/resource')
const finalResponse = await page.waitForResponse(
  response =>
    response.url() === 'https://example.com' && response.status() === 200
)
return finalResponse.ok()
await page.evaluate(() => window.open('https://www.example.com/'))
const newWindowTarget = await browserContext.waitForTarget(
  target => target.url() === 'https://www.example.com/'
)

Operation Simulation Testing​

const [response] = await Promise.all([
  page.waitForNavigation(waitOptions),
  page.click(selector, clickOptions),
])
// Using ‘page.mouse’ to trace a 100x100 square.
await page.mouse.move(0, 0)
await page.mouse.down()
await page.mouse.move(0, 100)
await page.mouse.move(100, 100)
await page.mouse.move(100, 0)
await page.mouse.move(0, 0)
await page.mouse.up()
await page.keyboard.type('Hello World!')
await page.keyboard.press('ArrowLeft')

await page.keyboard.down('Shift')
for (let i = 0; i < ' World'.length; i++) await page.keyboard.press('ArrowLeft')
await page.keyboard.up('Shift')

await page.keyboard.press('Backspace')
// Result text will end up saying 'Hello!'

Tracing Testing​

await page.tracing.start({ path: 'trace.json' })
await page.goto('https://www.google.com')
await page.tracing.stop()

Puppeteer Testing API​

  • page.setOfflineMode
  • page.setGeolocation
  • page.metrics
  • page.accessibility
  • page.coverage

Testing Frameworks​

Unit Testing Frameworks​

  • Jest.
  • Jasmine.
  • Mocha.

UI Testing Frameworks​

  • Cypress/PlayWright/Puppeteer.
  • 用户行为: Karma/Selenium.
  • 功能测试: Phantom.js/Slimer.js/Karma.

Testing Tools​

  • JUnit.
  • SeleniumIDE.
  • PICT.
  • GuiTar.
  • Randoop.
  • Apache Jmeter: 压力测试.
  • Monkey: Random testing.

Jest Testing​

Jest Installation​

npm i -D jest ts-jest @types/jest react-test-renderer

Jest Configuration​

jest.config.js:

const { pathsToModuleNameMapper } = require('ts-jest/utils')
const { compilerOptions } = require('./tsconfig.json')
const paths = pathsToModuleNameMapper(compilerOptions.paths, {
  prefix: '<rootDir>/',
})

/** @type {import('ts-jest/dist/types').InitialOptionsTsJest} */
module.exports = {
  roots: ['<rootDir>/src'],
  collectCoverage: true,
  coverageDirectory: 'coverage',
  transform: {
    '^.+\\.jsx?$': '<rootDir>/jest.transformer.js',
    '^.+\\.tsx?$': 'ts-jest',
  },
  transformIgnorePatterns: ['node_modules/(?!(gatsby)/)'],
  moduleFileExtensions: ['ts', 'tsx', 'js', 'jsx', 'json', 'node'],
  moduleNameMapper: {
    '.+\\.(css|styl|less|sass|scss)$': 'identity-obj-proxy',
    '.+\\.(jpg|jpeg|png|gif|eot|otf|webp|svg|ttf|woff|woff2|mp4|webm|wav|mp3|m4a|aac|oga)$':
      '<rootDir>/__mocks__/jest.mock.js',
    ...paths,
    '^@components/(.*)$': '<rootDir>/src/components/$1',
    '^@hooks/(.*)$': '<rootDir>/src/hooks/$1',
    '^@layouts/(.*)$': '<rootDir>/src/layouts/$1',
    '^@types/(.*)$': '<rootDir>/src/types/$1',
  },
  testPathIgnorePatterns: ['node_modules', '\\.cache', '<rootDir>.*/build'],
  testRegex: '(/__tests__/.*|(\\.|/)(test|spec))\\.(jsx?|tsx?)$',
  globals: {
    'window': {},
    'ts-jest': {
      tsConfig: './tsconfig.json',
    },
  },
  testURL: 'http://localhost',
  testEnvironment: 'jsdom',
  setupFiles: ['<rootDir>/jest.env.setup.js'],
  setupFilesAfterEnv: ['<rootDir>/jest.setup.js'],
  setupTestFrameworkScriptFile: '<rootDir>/src/setupEnzyme.ts',
}

jest.env.setup.js:

import path from 'node:path'
import dotenv from 'dotenv'

console.log(`============ env-setup Loaded ===========`)
dotenv.config({
  path: path.resolve(process.cwd(), 'tests', 'settings', '.test.env'),
})

jest.setup.js:

import '@testing-library/jest-dom'

// Global/Window object Stubs for Jest
window.matchMedia
  = window.matchMedia
  || function () {
    return {
      matches: false,
      addListener() {},
      removeListener() {},
    }
  }

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(),
  })),
})

window.requestAnimationFrame = function (callback) {
  setTimeout(callback)
}

window.cancelAnimationFrame = window.clearTimeout

window.localStorage = {
  getItem() {},
  setItem() {},
}

Object.values = () => []

vitest.config.ts:

import react from '@vitejs/plugin-react'
import { defineConfig } from 'vite'

export default defineConfig({
  plugins: [react()],
  test: {
    environment: 'jsdom',
    globals: true,
    setupFiles: './tests/setup.ts',
  },
})

tests/setup.ts:

import * as matchers from '@testing-library/jest-dom/matchers'
import { cleanup } from '@testing-library/react'
import { afterEach, expect } from 'vitest'

expect.extend(matchers)

afterEach(() => {
  cleanup()
})

setupEnzyme.ts:

import { configure } from 'enzyme'
import * as EnzymeAdapter from 'enzyme-adapter-react-16'

configure({ adapter: new EnzymeAdapter() })

Jest Basic Testing​

  • describe block.
  • test statement.
  • it statement.
  • test.todo:
    • Skip empty todo tests.
    • Skip temporary broken tests.
import { fireEvent, render, screen } from '@testing-library/react'
import LandingNav from './LandingNav'

describe('LandingNav', () => {
  test('should expanded when clicked', () => {
    render(<LandingNav />)

    expect(screen.getByRole('navigation')).toHaveStyle(
      'transform: translateX(-100%) translateZ(0);'
    )
    expect(screen.getByRole('banner')).toHaveStyle('opacity: 0')

    fireEvent.click(screen.getByTestId('hamburger-icon'))

    expect(screen.getByRole('navigation')).toHaveStyle(
      'transform: translateX(0%) translateZ(0);'
    )
    expect(screen.getByRole('banner')).toHaveStyle('opacity: 0.8')

    fireEvent.click(screen.getByTestId('hamburger-button'))

    expect(screen.getByRole('navigation')).toHaveStyle(
      'transform: translateX(-100%) translateZ(0);'
    )
    expect(screen.getByRole('banner')).toHaveStyle('opacity: 0')
  })
})

Use userEvent instead of fireEvent:

import userEvent from '@testing-library/user-event'

// setup userEvent
function setup(jsx) {
  return {
    user: userEvent.setup(),
    ...render(jsx),
  }
}

describe('Form', () => {
  it('should save correct data on submit', async () => {
    const mockSave = jest.fn()
    const { user } = setup(<Form saveData={mockSave} />)

    await user.type(screen.getByRole('textbox', { name: 'Name' }), 'Test')
    await user.click(screen.getByRole('button', { name: 'Sign up' }))

    expect(mockSave).toHaveBeenLastCalledWith({ ...defaultData, name: 'Test' })
  })
})

Use findBy instead of waitFor + getBy:

describe('ListPage', () => {
  it('renders without breaking', async () => {
    render(<ListPage />)
    expect(
      await screen.findByRole('heading', { name: 'List of items' }),
    ).toBeInTheDocument()
  })
})

Jest Snapshot Testing​

  • When you run jest first time, it will produce an snapshot file.
  • The next time run the tests, rendered output will be compared to previously created snapshot.
  • If change is expected, use jest -u to overwrite existing snapshot.
import { fireEvent, render, screen } from '@testing-library/react'
import ThemeSwitch from './ThemeSwitch'

describe('ThemeSwitch', () => {
  test('should switch dark mode when clicked', () => {
    const { container } = render(<ThemeSwitch />)

    fireEvent.click(screen.getByTestId('toggle-wrapper'))

    expect(container).toMatchSnapshot()
  })
})

Jest Async Testing​

Jest async guide:

await expect(asyncCall()).resolves.toEqual('Expected')
await expect(asyncCall()).rejects.toThrowError()

Jest Mocks​

Mocks

Jest Mocks Utils​

__mocks__:

  • jest.createMockFromModule('moduleName').
  • jest.requireActual('moduleName').

spyOn:

  • jest.spyOn().mockImplementation.
  • jest.spyOn().mockReturnValue.
  • jest.spyOn().mockReturnValueOnce.
  • jest.spyOn().mockResolvedValue.
  • jest.spyOn().mockRejectedValue.
  • mockModule.mockClear.
  • mockModule.mockReset.
  • mockModule.mockRestore.

Jest Module Mocks​

// react-dom.js
const reactDom = jest.requireActual('react-dom')

function mockCreatePortal(element, target) {
  return (
    <div>
      <div id="content">{element}</div>
      <div id="target" data-target-tag-name={target.tagName}></div>
    </div>
  )
}

reactDom.createPortal = mockCreatePortal

module.exports = reactDom
// gatsby.js
const gatsby = jest.requireActual('gatsby')

module.exports = {
  ...gatsby,
  graphql: jest.fn(),
  Link: jest
    .fn()
    .mockImplementation(
      ({
        activeClassName,
        activeStyle,
        getProps,
        innerRef,
        partiallyActive,
        ref,
        replace,
        to,
        ...rest
      }) =>
        React.createElement('a', {
          ...rest,
          href: to,
        })
    ),
  StaticQuery: jest.fn(),
  useStaticQuery: jest.fn(),
}

Jest Date Mocks​

jest
  .spyOn(Date.prototype, 'toISOString')
  .mockReturnValue('2020-06-20T13:37:00.000Z')

Jest API Mocks​

import { rest } from 'msw'
import { setupServer } from 'msw/node'

const handlers = [
  rest.get('https://mysite.com/api/role', async (req, res, ctx) => {
    res(ctx.status(200), ctx.json({ userType: 'user' }))
  }),
]

const server = setupServer(...handlers)

export default server
import server from './mockServer/server'

beforeAll(() => {
  server.listen()
})

afterEach(() => {
  server.resetHandlers()
})

afterAll(() => {
  server.close()
})
import type { UserRoleType } from './apis/user'
import { render, screen } from '@testing-library/react'
import { rest } from 'msw'
import AuthButton from './components/AuthButton'
import server from './mockServer/server'

function setup(userType: UserRoleType) {
  server.use(
    rest.get('https://mysite.com/api/role', async (req, res, ctx) => {
      return res(ctx.status(200), ctx.json({ userType }))
    })
  )
}

describe('AuthButton', () => {
  it('should render user text', async () => {
    setup('user')

    render(<AuthButton>Hello</AuthButton>)

    expect(await screen.findByText('Hello User')).toBeInTheDocument()
  })

  it('should render admin text', async () => {
    setup('admin')

    render(<AuthButton>Hello</AuthButton>)

    expect(await screen.findByText('Hello Admin')).toBeInTheDocument()
  })
})

Jest Internals​

Jest Runtime Sandbox​

Running tests in ShadowRealms:

// demo.test.js
import { test } from './TestLib.js'

test('succeeds', () => {
  assert.equal(3, 3)
})

test('fails', () => {
  assert.equal(1, 3)
})

// This statement can add by `babel`.

export default true

// TestLib.js
const testSuites = []

export function test(description, callback) {
  testSuites.push({ description, callback })
}

export function runTests() {
  const testResults = []

  for (const testSuite of testSuites) {
    try {
      testSuite.callback()
      testResults.push(`${testSuite.description}: OK\n`)
    } catch (err) {
      testResults.push(`${testSuite.description}: ${err}\n`)
    }
  }

  return testResults.join('')
}

// TestRunner.js
async function runTestModule(moduleSpecifier) {
  const sr = new ShadowRealm()
  await sr.importValue(moduleSpecifier, 'default')
  const runTests = await sr.importValue('./TestLib.js', 'runTests')
  const result = runTests()
  console.log(result)
}

await runTestModule('./demo.test.js')

Jest Test Runner​

A simple test runner implementation:

import { promises as fs } from 'node:fs'
import { basename, dirname, join } from 'node:path'
import { pathToFileURL } from 'node:url'

async function* walk(dir: string): AsyncGenerator<string> {
  for await (const d of await fs.opendir(dir)) {
    const entry = join(dir, d.name)

    if (d.isDirectory())
      yield * walk(entry)
    else if (d.isFile())
      yield entry
  }
}

async function runTestFile(file: string): Promise<void> {
  for (const value of Object.values(
    await import(pathToFileURL(file).toString())
  )) {
    if (typeof value === 'function') {
      try {
        await value()
      } catch (e) {
        console.error(e instanceof Error ? e.stack : e)
        process.exit(1)
      }
    }
  }
}

async function run(arg = '.') {
  if ((await fs.lstat(arg)).isFile())
    return runTestFile(arg)

  for await (const file of walk(arg)) {
    if (
      !dirname(file).includes('node_modules')
      && (basename(file) === 'test.js' || file.endsWith('.test.js'))
    ) {
      console.log(file)
      await runTestFile(file)
    }
  }
}

run(process.argv[2])

Jest Native Runner​

Implement component testing with native node:test module:

import assert from 'node:assert'
import test from 'node:test'
import { cleanup, render } from '@testing-library/react'
import jsdom from 'jsdom'

const j = new jsdom.JSDOM(undefined, {
  url: 'http://localhost', // Many APIs are confused without being "on a real URL"
  pretendToBeVisual: true, // This adds dummy requestAnimationFrame and friends
})

// We need to add everything on JSDOM's window object to global scope.
// We don't add anything starting with _, or anything that's already there.
Object.getOwnPropertyNames(j.window)
  .filter(k => !k.startsWith('_') && !(k in globalThis))
  .forEach(k => (globalThis[k] = j.window[k]))

// Finally, tell React 18+ that we are not really a browser.
globalThis.IS_REACT_ACT_ENVIRONMENT = true

function reactTest(name, fn) {
  return test(name, () => {
    cleanup() // always cleanup first
    return fn()
  })
}

export default function FooComponent({ text }: { text: string }) {
  return (
    <div>
      Hello
      {' '}
      <span data-testid="hold">{text}</span>
    </div>
  )
}

reactTest('test component', () => {
  const result = render(<FooComponent name={Sam} />)
  assert.strictEqual(result.getByTestId('hold').textContent, 'Sam')
})

Jest Performance​

Jest 的整体架构, 其中有 3 个地方比较耗性能:

  • 生成虚拟文件系统 (jest-haste-map): 在跑第一个测试会很慢.
  • 多线程: 生成新线程耗费的资源.
  • 文件转译: Jest 会在执行到该文件再对它进行转译. 使用 esbuild-jest/@swc/jest 加速转译.

Jest Plugins​

  • Jest debug tool.
  • Jest visual regression testing tool.

Jest Best Practices​

Cypress Testing​

When it comes to test heavy visual features, (e.g fixed navigation based on window scroll event), E2E testing helps a lot.

Cypress Installation​

yarn add -D cypress typescript
yarn cypress open

cypress open will initialize the cypress folder structure.

Cypress Configuration​

cypress/tsconfig.json:

{
  "extends": "../tsconfig.json",
  "include": ["global.d.ts", "**/*.ts"],
  "exclude": [],
  "compilerOptions": {
    "strict": true,
    "target": "ES6",
    "lib": ["ES6", "DOM"],
    "types": ["cypress"],
    "isolatedModules": false,
    "noEmit": true
  }
}

cypress/global.d.ts:

/// <reference types="cypress" />

cypress.config.ts:

import { defineConfig } from 'cypress'

export default defineConfig({
  e2e: {
    baseUrl: 'http://localhost:3000',
  },
})

tsconfig.json:

{
  "include": ["next-env.d.ts", "**/*.ts", "**/*.tsx"],
  "exclude": ["node_modules", "cypress"]
}

package.json:

{
  "scripts": {
    "e2e:chrome": "start-server-and-test e2e:prepare http://localhost:3000 cypress:chrome",
    "e2e:firefox": "start-server-and-test e2e:prepare http://localhost:3000 cypress:firefox",
    "e2e:ui": "start-server-and-test e2e:prepare http://localhost:3000 cypress:open",
    "e2e:prepare": "yarn build && yarn serve",
    "cypress:chrome": "cypress run --browser chrome",
    "cypress:chromium": "cypress run --browser chromium",
    "cypress:edge": "cypress run --browser edge",
    "cypress:electron": "cypress run",
    "cypress:firefox": "cypress run --browser firefox",
    "cypress:open": "cypress open --browser electron --e2e"
  }
}

.gitignore:

# cypress files
cypress/screenshots
cypress/videos

jest.config.js:

const config = {
  testPathIgnorePatterns: ['/node_modules/', '/.next/', '/cypress/'],
}

Basic Cypress Testing​

cypress/support/commands.ts:

import '@testing-library/cypress/add-commands'

cypress/e2e/component.cy.ts:

/// <reference types="cypress"/>

describe('component', () => {
  it('should work', () => {
    cy.visit('/')
    cy.get('#onOff')
      .should('have.text', 'off')
      .click()
      .should('have.text', 'on')
  })
})

cypress/e2e/payment.cy.ts:

import { v4 as uuid } from 'uuid'

describe('payment', () => {
  it('user can make payment', () => {
    //  Login.
    cy.visit('/')
    cy.findByRole('textbox', { name: /username/i }).type('sabertaz')
    cy.findByLabelText(/password/i).type('secret')
    cy.findByRole('checkbox', { name: /remember me/i }).check()
    cy.findByRole('button', { name: /sign in/i }).click()

    // Check account balance.
    let oldBalance
    cy.get('[data-test=nav-user-balance]').then(
      $balance => (oldBalance = $balance.text())
    )

    // Click on new button.
    cy.findByRole('button', { name: /new/i }).click()

    // Search for user.
    cy.findByRole('textbox').type('devon becker')
    cy.findByText(/devon becker/i).click()

    // Add amount and note and click pay.
    const paymentAmount = '5.00'
    cy.findByPlaceholderText(/amount/i).type(paymentAmount)
    const note = uuid()
    cy.findByPlaceholderText(/add a note/i).type(note)
    cy.findByRole('button', { name: /pay/i }).click()

    // Return to transactions.
    cy.findByRole('button', { name: /return to transactions/i }).click()

    // Go to personal payments.
    cy.findByRole('tab', { name: /mine/i }).click()

    // Click on payment.
    cy.findByText(note).click({ force: true })

    // Verify if payment was made.
    cy.findByText(`-$${paymentAmount}`).should('be.visible')
    cy.findByText(note).should('be.visible')

    // Verify if payment amount was deducted.
    cy.get('[data-test=nav-user-balance]').then(($balance) => {
      const convertedOldBalance = Number.parseFloat(oldBalance.replace(/\$|,/g, ''))
      const convertedNewBalance = Number.parseFloat(
        $balance.text().replace(/\$|,/g, '')
      )
      expect(convertedOldBalance - convertedNewBalance).to.equal(
        Number.parseFloat(paymentAmount)
      )
    })
  })
})

Cypress Principles​

  • Flake resistance and retry-ability: don't wait for fixed time, wait for specific elements (cy.as): cy.get/cy.find/cy.its/cy.should commands will give the page an opportunity to fully load, and then the tests can proceed (Cypress run in browser directly).
  • Asynchronous nature: use cy.then/cy.wrap for async nature of Cypress.

Cypress Commands​

Cypress Basic Commands​

  • cy.its: get property value on previously yielded subject.
  • cy.invoke: invoke function on previously yielded subject.
cy.wrap(['Wai Yan', 'Yu']).its(1).should('eq', 'Yu')
cy.wrap({ age: 52 }).its('age').should('eq', 52)
cy.wait('@publicTransactions')
  .its('response.body.results')
  .invoke('slice', 0, 5)

Cypress Action Commands​

  • cy.click.
  • cy.dbclick.
  • cy.type.
  • cy.clear.
  • cy.focus.
  • cy.blur.
  • cy.check.
  • cy.uncheck.
  • cy.select.
  • cy.selectFile.
  • cy.submit.
  • cy.trigger.
  • cy.scrollTo.
  • cy.scrollIntoView.

Cypress Network Commands​

  • cy.intercept: mock API response.
cy.intercept('GET', '/transactions/public*', {
  fixture: 'public-transactions.json',
}).as('mockedPublicTransactions')

cy.wait('@mockedPublicTransactions')

cy.intercept('GET', '/transactions/public*', {
  headers: {
    'X-Powered-By': 'Express',
    'Date': new Date().toString(),
  },
})

cy.intercept('POST', '/bankAccounts', (req) => {
  const { body } = req
  req.continue((res) => {
    res.body.data.listBankAccount = []
  })
})

cy.intercept('POST', apiGraphQL, (req) => {
  const { body } = req

  if (
    Object.hasOwn(body, 'operationName')
    && body.operationName === 'CreateBankAccount'
  ) {
    req.alias = 'gqlCreateBankAccountMutation'
  }
})
  • cy.request: API integration/E2E tests.
Cypress.Commands.add('getAllPosts', () => {
  return cy.request('GET', '/api/posts').then((response) => {
    return cy.wrap(response.body)
  })
})

Cypress.Commands.add('getFirstPost', () => {
  return cy.request('GET', '/api/posts').then((response) => {
    return cy.wrap(response.body).its(0)
  })
})

describe('GET', () => {
  it('gets a list of users', () => {
    cy.request('GET', '/users').then((response) => {
      expect(response.status).to.eq(200)
      expect(response.body.results).length.to.be.greaterThan(1)
    })
  })

  it('gets a list of comments', () => {
    cy.request('/comments').as('comments')

    cy.get('@comments').should((response) => {
      expect(response.body).to.have.length(500)
      expect(response).to.have.property('headers')
      expect(response).to.have.property('duration')
    })
  })
})

Cypress Custom Command​

/// <reference types="cypress" />

declare global {
  namespace Cypress {
    interface Chainable {
      findByRole: (role: string) => Chainable<JQuery<HTMLElement>>
      findByTestId: (testId: string) => Chainable<JQuery<HTMLElement>>
      getByRole: (role: string) => Chainable<JQuery<HTMLElement>>
      getByTestId: (testId: string) => Chainable<JQuery<HTMLElement>>
    }
  }
}

Cypress.Commands.add(
  'findByRole',
  { prevSubject: 'element' },
  (subject, role) => {
    return cy.wrap(subject, { log: false }).find(`[role="${role}"]`)
  }
)

Cypress.Commands.add(
  'findByTestId',
  { prevSubject: 'element' },
  (subject, testId) => {
    return cy.wrap(subject, { log: false }).find(`[data-testid="${testId}"]`)
  }
)

Cypress.Commands.add('getByRole', (role) => {
  return cy.get(`[role="${role}"]`)
})

Cypress.Commands.add('getByTestId', (testId) => {
  return cy.get(`[data-testid="${testId}"]`)
})

Custom command log:

Cypress.Commands.add('take', (input: string) => {
  let element: JQuery<HTMLElement> | HTMLElement[]
  let count: number

  const log = Cypress.log({
    autoEnd: false,
    consoleProps() {
      return {
        selector: input,
        Yielded: element,
        Elements: count,
      }
    },
    displayName: 'take',
    name: 'Get by [data-cy] attribute',
  })

  cy.get(`[data-cy=${input}]`, { log: false }).then(($el) => {
    element = Cypress.dom.getElements($el)
    count = $el.length
    log.set({ $el })
    log.snapshot().end()
  })

  cy.on('fail', (err) => {
    log.error(err)
    log.end()
    throw err
  })
})

Cypress Plugin​

Setup TypeScript to transpile tests:

import wp from '@cypress/webpack-preprocessor'
// cypress.config.ts
import { defineConfig } from 'cypress'

export default defineConfig({
  e2e: {
    setupNodeEvents(on, config) {
      on(
        'file:preprocessor',
        wp({
          webpackOptions: {
            resolve: {
              extensions: ['.ts', '.tsx', '.js', '.jsx'],
            },
            module: {
              rules: [
                {
                  test: /\.tsx?$/,
                  loader: 'ts-loader',
                  options: { transpileOnly: true },
                },
              ],
            },
          },
        })
      )
    },
  },
})

AXE a11y testing:

// cypress.config.ts
import { defineConfig } from 'cypress'
import fetch from 'undici'

export default defineConfig({
  e2e: {
    setupNodeEvents(on, config) {
      on('task', {
        sitemapLocations() {
          return fetch(`${config.baseUrl}/sitemap.xml`, {
            method: 'GET',
            headers: {
              'Content-Type': 'application/xml',
            },
          })
            .then(res => res.text())
            .then((xml) => {
              const locs = [...xml.matchAll(`<loc>(.|\n)*?</loc>`)].map(
                ([loc]) => loc.replace('<loc>', '').replace('</loc>', '')
              )
              return locs
            })
        },
      })

      return config
    },
  },
})

// cypress/e2e/smoke.cy.ts
it('should be accessible', () => {
  cy.task('sitemapLocations').then((pages) => {
    pages.forEach((page) => {
      cy.visit(page)
      cy.injectAxe()
      cy.checkA11y(
        {
          exclude: ['.article-action'],
        },
        {
          rules: {
            'empty-heading': { enabled: false },
            'scrollable-region-focusable': { enabled: false },
          },
        }
      )
    })
  })
})
  • Cypress code coverage plugin.
  • Cypress commands plugin.
  • Cypress events plugin.
  • Cypress accessibility testing plugin.
  • Cypress visual regression testing plugin.

Cypress Reference​

Debugging​

Monkey Patch​

Window State Injection​

Inject trace function (log, monitor, report service) to window pushState and replaceState.

const _wr = function (type) {
  const orig = window.history[type]

  return function (...args) {
    const rv = orig.apply(this, args)
    const e = new Event(type.toLowerCase())
    e.arguments = args
    window.dispatchEvent(e)
    return rv
  }
}

window.history.pushState = _wr('pushState')
window.history.replaceState = _wr('replaceState')

window.addEventListener('pushstate', (event) => {
  console.trace('pushState')
})

window.addEventListener('replacestate', (event) => {
  console.trace('replaceState')
})

Event Propagation Injection​

const originalStopPropagation = MouseEvent.prototype.stopPropagation

MouseEvent.prototype.stopPropagation = function (...args) {
  console.trace('stopPropagation')
  originalStopPropagation.call(this, ...args)
}

Window Scroll Injection​

let originalScrollTop = element.scrollTop

Object.defineProperty(element, 'scrollTop', {
  get() {
    return originalScrollTop
  },
  set(newVal) {
    console.trace('scrollTop')
    originalScrollTop = newVal
  },
})

Logging​

Logging Type​

  • Application client log.
  • Web server log.
  • Database server log.
  • Access log.
  • Debug log.
  • Error log.

Logging Information​

  • 日志时间: 包含时区信息和毫秒.
  • 日志级别.
  • 会话标识.
  • 功能标识.
  • 精炼内容: 场景信息, 状态信息 (开始/中断/结束), 重要参数.
  • 其他信息: 版本号, 线程号.

Logging Setup​

const { createLogger, format, transports } = require('winston')

const logLevels = {
  fatal: 0,
  error: 1,
  warn: 2,
  info: 3,
  debug: 4,
  trace: 5,
}

const logger = createLogger({
  levels: logLevels,
  format: format.combine(format.timestamp(), format.json()),
  transports: [new transports.Console()],
})

logger.info('System Started')
logger.fatal('Fatal error occurred')

Logging Clock​

  • performance.now() is more precise (100 us).
  • performance.now() is strictly monotonic (unaffected by changes of machine time).
let lastVisibilityChange = 0

window.addEventListener('visibilitychange', () => {
  lastVisibilityChange = performance.now()
})

// don’t log any metrics started before the last visibility change
// don't log any metrics if the page is hidden
// discard perf data from when the machine was not running app at full speed
function metrics() {
  if (metric.start < lastVisibilityChange || document.hidden)
    return

  process()
}
requestAnimationFrame(() => {
  requestAnimationFrame((timestamp) => {
    metric.finish(timestamp)
  })
})

Console API​

  • console.XXX.
  • copy: copy complex object to clipboard.
  • monitor: monitor object.
const devtools = /./
devtools.toString = function () {
  this.opened = true
}

console.log('%c', devtools)
// devtools.opened will become true if/when the console is opened
// Basic console functions
console.assert()
console.clear()
console.log()
console.debug()
console.info()
console.warn()
console.error()

// Different output styles
console.dir()
console.dirxml()
console.table()
console.group()
console.groupCollapsed()
console.groupEnd()

// Trace console functions
console.trace()
console.count()
console.countReset()
console.time()
console.timeEnd()
console.timeLog()

// Non-standard console functions
console.profile()
console.profileEnd()
console.timeStamp()

console.log:

// `sprinf` style log
console.log('%d %o %s', integer, object, string)
console.log('%c ...', 'css style')

console.table:

// display array of object (tabular data)
const transactions = [
  {
    id: '7cb1-e041b126-f3b8',
    seller: 'WAL0412',
    buyer: 'WAL3023',
    price: 203450,
    time: 1539688433,
  },
  {
    id: '1d4c-31f8f14b-1571',
    seller: 'WAL0452',
    buyer: 'WAL3023',
    price: 348299,
    time: 1539688433,
  },
  {
    id: 'b12c-b3adf58f-809f',
    seller: 'WAL0012',
    buyer: 'WAL2025',
    price: 59240,
    time: 1539688433,
  },
]

console.table(data, ['id', 'price'])

JavaScript Tracing API​

debugger:

// debugger;
copy(obj) // to clipboard
window.onerror = function (errorMessage, scriptURI, lineNo, columnNo, error) {
  console.log(`errorMessage: ${errorMessage}`) // 异常信息
  console.log(`scriptURI: ${scriptURI}`) // 异常文件路径
  console.log(`lineNo: ${lineNo}`) // 异常行号
  console.log(`columnNo: ${columnNo}`) // 异常列号
  console.log(`error: ${error}`) // 异常堆栈信息
  // ...
  // 异常上报
}

window.addEventListener('error', () => {
  console.log(error)
  // ...
  // 异常上报
})

Trace Property​

function traceProperty(object, property) {
  let value = object[property]
  Object.defineProperty(object, property, {
    get() {
      console.trace(`${property} requested`)
      return value
    },
    set(newValue) {
      console.trace(`setting ${property} to `, newValue)
      value = newValue
    },
  })
}

Node Debugging API​

  • node --inspect.
  • ndb.
node --inspect
ndb index.js

Chrome DevTools​

DevTools Detection​

Console DevTools Detection​

const x = document.createElement('div')

Object.defineProperty(x, 'id', {
  get() {
    // devtool opened.
    return 'id'
  },
})

console.log(x)
// eslint-disable-next-line prefer-regex-literals
const c = new RegExp('1')

c.toString = function () {
  // devtool opened
}

console.log(c)

Anti Method: hook console object, disable all outputs.

Debugger Detection​

;(function () {}).constructor('debugger')()
;(() => {
  function block() {
    if (
      window.outerHeight - window.innerHeight > 200
      || window.outerWidth - window.innerWidth > 200
    ) {
      document.body.innerHTML = 'Debug detected, please reload page!'
    }

    setInterval(() => {
      ;(function () {
        return false
      })
        .constructor('debugger')
        .call()
    }, 50)
  }

  try {
    block()
  } catch (err) {}
})()
const startTime = new Date()
// debugger;
const endTime = new Date()
const isDev = endTime - startTime > 100

while (true) {
  // debugger;
}

Anti Method: use chrome protocol to block all debugger request. Anti Method: hook Function.prototype.constructor and replace debugger string.

Chrome DevTools Shortcuts​

  • c-d: go to next word
  • c-f in Elements panel: search DOM node
  • c-m: go to next bracket
  • c-p: go to files
  • cs-p: go to anywhere
  • cs-o: go to functions

long click reload: multiple reload options e.g clean cache

Elements Panel​

  • Break on elements.
  • Inspect elements a11y.

Style Tab​

  • color picker
  • filter: class filter, pseudo filter, css style filter

Console Panel​

Console utilities API:

  • $_.
  • $0 - $4.
  • $(): document.querySelector().
  • $$(): document.querySelectorAll().
  • getEventListeners(dom).
  • monitorEvents(dom, events).
  • unmonitorEvents(dom).
  • monitor(fn).
  • unmonitor(fn).
  • debug(fn).
  • undebug(fn).
  • keys(object).
  • values(object).
  • queryObjects(Constructor).

Console Settings​

  • preserve log
  • show timestamps
  • Verbose: additional performance log
  • click filename, filter error messages
  • add folder to workspace

Capture Default Event Listener​

$0: the reference to the currently selected element in the Elements panel.

const listener = getEventListeners($0).click[0].listener
$0.removeEventListener('click', listener)
$0.addEventListener('click', (e) => {
  // do something
  // ...

  // then
  listener(e)
})

Source Panel​

  • Add log points.
  • Multiple breakpoints: source, XHR/fetch, DOM, global/event listeners.
  • Open a source file, right click code, Blackbox script item.
  • Local Overrides for persistent changes to css styles.

Same thing in VSCode debug panel (log points, break points etc).

Network Panel​

  • throttling: simulate different network environment.
  • initiator: go to files.

Performance Panel​

  • C+S+P: performance monitor.
  • C+S+P: FPS.
  • Performance tips.
  • Memory panel.
  • Timeline events: script -> style -> layout -> paint -> composite.
  • Timeline events reference.
  • Performance analysis reference.
  • Performance tools guide.

Simulation DevTools​

  • cs-p: type 3G (slow network)
  • cs-p: type sensor (geolocation)

Audit DevTool​

  • cs-p: type audit

Coverage Tool​

  • cs-p: type coverage
  • Use to eliminate unused CSS/JS code.

Memory Panel​

  • Heap snapshot

JS Profiler Panel​

Layer Panel​

Tool for composite stage analysis:

  • Compositor layers.

Rendering Panel​

  • FPS monitor.
  • Scroll event.
  • Paint flashing area: re-paint area.
  • Compositor layers border.
  • Layout shift region.
  • CSS media query emulation:
    • prefers-color-scheme.
    • prefers-reduced-motion.
    • prefers-contrast.
    • A11y emulation.

Animation Panel​

  • Animations.

Bug List​

Basic Bug​

  • 必须进行输入验证 - 永远不要相信用户输入.
  • 永不使用未经验证的数值的长度或大小.
  • 必须返回正确的错误状态.
  • 注意(隐式)类型转换.

C Bug​

  • 栈缓冲区溢出.
  • 空指针解引用.
  • (隐式)类型转换.
  • GOT 覆写 (Global Offset Table).

Occasional Bug​

  • 多进程完全异步编程的复杂性.
  • 逐渐地内存泄漏.

Reference​