Jest
简单测试
js
// demo.js
function sum (a, b) {
return a + b;
}
function subtract (x, y) {
return x - y;
}
module.exports = {
sum,
subtract
}
js
// demo.test.js
// 1. 引入测试函数
const { sum, subtract } = require('./demo');
// 2. 定义函数输入
const result = sum(1, 2);
// 3. 定义预期输出
const expected = 3;
// 4. 检查函数是否返回预期结果
if (result !== expected) {
throw new Error(`sum(1, 2) result ${ expected }, but get ${ result }`);
}
断言和测试用例
定义 expect 断言函数
js
const { sum, subtract } = require('./demo');
expect(sum(1, 2)).toBe(3);
function expect (result) {
return {
toBe (expected) {
if (result !== expected) {
throw new Error(`expect result ${ expected }, but get ${ result }`);
}
}
}
}
js
const { sum, subtract } = require('./demo');
expect(sum(1, 2)).toBe(3);
expect(subtract(2, 1)).toBe(1);
function expect (result) {
return {
toBe (expected) {
if (result !== expected) {
throw new Error(`expect result ${ expected }, but get ${ result }`);
}
}
}
}
定义 test 函数，test 函数其实就是测试用例，一个测试用例可以包含多个断言函数。
js
test('sum(1, 2) result is 3', () => {
expect(sum(1, 2)).toBe(3);
})
test('subtract(2, 1) result is 1', () => {
expect(subtract(2, 1)).toBe(1);
})
function test (message, callback) {
try {
callback();
} catch (error) {
console.error(`${ message }: ${ error }`);
}
}
function expect (result) {
return {
toBe (expected) {
if (result !== expected) {
throw new Error(`expect result ${ expected }, but get ${ result }`);
}
}
}
}
Jest 体验
安装、使用
初始化 package.json、安装 jest
js
pnpm init -y
pnpm i jest -D
定义 scripts 脚本
js
// package.json
{
"scripts": {
"test": "jest"
},
}
运行测试脚本
js
pnpm run test
js
PASS ./demo.test.js
√ sum(1, 2) result is 3 (2 ms)
√ subtract(2, 1) result is 1
Test Suites: 1 passed, 1 total
Tests: 2 passed, 2 total
Snapshots: 0 total
Time: 0.401 s, estimated 1 s
Ran all test suites.
jest 在运行 *.test.js 文件时，会把 test、expect 等相关辅助函数注册到全局环境。
增加代码提示
js
pnpm i @types/jest -D
安装 @types 模块后，可以直接使用 jest 提示，无须引入。
Jest 介绍
Jest 是 Facebook 出品的一个 JavaScript 开源测试框架。相对其他测试框架，它最大特点就是内置了常用的测试工具，比如零配置、自带断言、测试覆盖率等功能，实现了开箱即用。
Jest 使用但不限于以下技术项目：Babel、TypeScript、Node、React、Angular、Vue 等。
Jest 特点：
- 零配置
- 自带断言
- 作为一个面向前端的测试框架，Jest 可以利用其特有的快照测试功能，通过比对 UI 代码生成的快照文件，实现对 React 等常见框架的自动化测试
- Jest 的测试用例是并行执行的，只执行发生改变的文件所对应的测试
- 测试覆盖率
- Mock 模拟
配置文件
Jest 提供默认的零配置的使用方式，不过我们可以通过配置文件的方式去更改默认配置。
生成配置文件
js
npx jest --init
配置文件中会生成所有配置，不过大部分都是默认配置。
js
// jest.config.js
/*
* For a detailed explanation regarding each configuration property, visit:
* https://jestjs.io/docs/configuration 官方文档地址
*/
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: "C:\\Users\\yueluo\\AppData\\Local\\Temp\\jest",
// 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: false,
// 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: undefined,
// 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>"
// ],
// 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: [],
// 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,
// 默认文件配置规则
// The glob patterns Jest uses to detect test files
// testMatch: [
// "**/__tests__/**/*.[jt]s?(x)",
// "**/?(*.)+(spec|test).[tj]s?(x)"
// ],
// 默认忽略目录
// 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,
};
JestCli 选项
Jest 不仅可以通过配置文件配置，还可以通过命令行参数进行配置。
js
// a.test.js
test('test a', () => {
console.log('this a');
})
js
// demo.test.js
const { sum, subtract } = require('./demo');
test('sum(1, 2) result is 3', () => {
expect(sum(1, 2)).toBe(3);
})
test('subtract(2, 1) result is 1', () => {
expect(subtract(2, 1)).toBe(1);
})
直接运行 pnpm run test 会执行所有的测试用例。
js
> 02@1.0.0 test
> jest
PASS ./a.test.js
● Console
console.log
this a
at Object.log (a.test.js:2:11)
PASS ./demo.test.js
Test Suites: 2 passed, 2 total
Tests: 3 passed, 3 total
Snapshots: 0 total
Time: 1.58 s
Ran all test suites.
我们还可以指定需要测试的文件
js
// package.json
{
"scripts": {
"test": "jest",
"test2": "jest demo.test.js"
}
}
执行 pnpm run test2 只会执行 demo.test.js 文件。
js
PASS ./demo.test.js
√ sum(1, 2) result is 3 (1 ms)
√ subtract(2, 1) result is 1
Test Suites: 1 passed, 1 total
Tests: 2 passed, 2 total
Snapshots: 0 total
Time: 0.454 s, estimated 1 s
Ran all test suites matching /demo.test.js/i.
现在 jest 只会在手动执行的时候触发，如果我们向实时监听文件变化可以这样配置。
js
// package.json
{
"scripts": {
// ...
"test:watch": "jest --watchAll"
}
}
运行脚本文件，jest 就会监听所有文件的执行。
js
> 02@1.0.0 test
> jest
PASS ./a.test.js
● Console
console.log
this a
at Object.log (a.test.js:2:11)
PASS ./demo.test.js
PASS ./a.test.js
● Console
console.log
this a
at Object.log (a.test.js:2:11)
Test Suites: 2 passed, 2 total
Tests: 3 passed, 3 total
Snapshots: 0 total
Time: 1.109 s
Ran all test suites.
Watch Usage
› Press f to run only failed tests.
› Press o to only run tests related to changed files.
› Press p to filter by a filename regex pattern.
› Press t to filter by a test name regex pattern.
› Press q to quit watch mode.
› Press Enter to trigger a test run.
建议开发过程中使用 watch 模式，可以实时给予反馈。
监视模式
--watchAll
监视文件的更改并在任何更改时重新运行所有的测试文件。
js
jest --watchAll
--watch
该模式需要 Git 支持
监视 Git 仓库中的文件更改，并重新运行已更改文件相关的测试。如果文件未更改，不会执行任何测试文件。
js
jest --watch
监视模式的服务命令
执行 jest --watchAll 后，会打印出如下内容：
js
Watch Usage
› Press f to run only failed tests.
› Press o to only run tests related to changed files.
› Press p to filter by a filename regex pattern.
› Press t to filter by a test name regex pattern.
› Press q to quit watch mode.
› Press Enter to trigger a test run.
执行脚本后，可以通过键盘控制 jest。
- f：只运行失败的测试
- o：只运行与更改文件相关的测试，即 watch模式（需要 git 支持）
- a：运行所有的测试，即 watchAll 模式
- p：以文件名正则表达式模式进行过滤
- 只有 --watchAll 的时候 p 模式才生效
- 注意：testRegex 将尝试使用绝对路径的方式来检测
- t：根据测试名称进行过滤，即
test('sum')，sum 就是测试名称 - q：退出监视模式
- enter：触发测试重新执行
使用 ES6 模块
Jest 在运行测试的时候会自动找到 Babel 将 ES6 代码转换为 ES5 执行。
运行原理：运行测试之前，结合 Babel，先把你的代码做一次转化，模块被转换为 CommonJS，运行转换后的测试用例代码。
js
pnpm install babel-jest @babel/core @babel/preset-env -D
js
// babel.config.js
module.exports = {
presets: [
['@babel/preset-env', { targets: { node: 'current' } }],
]
}
js
// demo.js
export function sum (a, b) {
return a + b;
}
export function subtract (x, y) {
return x - y;
}
js
// demo.test.js
import { sum, subtract } from './demo';
test('sum(1, 2) result is 3', () => {
expect(sum(1, 2)).toBe(3);
})
test('subtract(2, 1) result is 1', () => {
expect(subtract(2, 1)).toBe(1);
})
执行脚本文件 pnpm run test2 可以正常运行。
js
> 02@1.0.0 test2 D:\workspace\notes\jest\02
> jest demo.test.js
PASS ./demo.test.js
√ sum(1, 2) result is 3 (1 ms)
√ subtract(2, 1) result is 1
Test Suites: 1 passed, 1 total
Tests: 2 passed, 2 total
Snapshots: 0 total
Time: 2.086 s
Ran all test suites matching /demo.test.js/i.
Jest API
测试文件中，Jest 将所有的方法和对象放入到全局环境中，不需要导入任何内容就可以使用。不过也支持显式导入。
js
pnpm i @jest/globals -D
js
import { describe, expect, test } from '@jest/globals';
Test 函数
test 函数别名：it(name, fn, timeout)，test 函数就是一个测试用例。
test(name, fn, timeout)test.concurrent(name, fn, timeout)test.concurrent.each(table)(name, fn, timeout)test.concurrent.only.each(table)(name, fn)test.each(table)(name, fn, timeout)test.only(name, fn, timeout)：仅运行当前测试用例（针对当前模块）
Expect 匹配器
编写测试前，通常需要检查值是否满足某些条件。Expect 支持访问许多 “匹配器”，以验证不同的内容。
js
test('global expect', () => {
expect(2 + 2).toBe(4); // 匹配数字
expect({ name: 'jack' }).toEqual({ name: 'jack' }); // 匹配对象
expect('yueluosensen').toMatch(/yueluo/); // 正则匹配
expect(4).toBeGreaterThan(2); // 大于
expect(4).toBeLessThan(5); // 小于
})
更多用法：https://jestjs.io/docs/expect
describe 函数
describe 创建一个将几个测试组合在一起的块。
js
describe('demo', () => {
test('sum(1, 2) result is 3', () => {
expect(sum(1, 2)).toBe(3);
})
test('subtract(2, 1) result is 1', () => {
expect(subtract(2, 1)).toBe(1);
})
})
describe('global', () => {
test('global expect', () => {
expect(2 + 2).toBe(4); // 匹配数字
expect({ name: 'jack' }).toEqual({ name: 'jack' }); // 匹配对象
expect('yueluosensen').toMatch(/yueluo/); // 正则匹配
expect(4).toBeGreaterThan(2); // 大于
expect(4).toBeLessThan(5); // 小于
})
})
如果测试用例同时写在一个文件中，可以将相关的测试用例进行分组。
相关用法：
describe(name, fn)describe.each(table)(name, fn, timeout)describe.only(name, fn)describe.only.each(table)(name, fn)describe.skip(name, fn)describe.skip.each(table)(name, fn)
生命周期钩子
beforeAll(fn, timeout)：测试用例之前执行（仅运行一次）beforeEach(fn, timeout)：每个测试用例运行之前，都会执行一次afterAll(fn, timeout)：测试用例执行完毕执行（仅运行一次）afterEach(fn, timeout)：每个测试用例执行完毕之后，都会执行一次
Jest 对象
Jest 对象自动位于每个测试文件中的范围内。
jest 对象中的方法有助于创建模拟，可以控制 Jest 的整体行为。也可以手动导入。
js
// jest.autoMockOn
// jest.useFakeTimers
详情内容参考：https://jestjs.io/docs/jest-object。
常用匹配器
https://jestjs.io/docs/using-matchers。
Common Matchers
js
describe('common matchers', () => {
test('two plus two is four', () => {
expect(2 + 2).toBe(4);
expect('hello').toBe('hello');
expect(true).toBe(true);
const author = { name: 'yueluo' };
expect(author).toBe(author); // toBe 只可以判断对象引用
expect({ name: 'yueluo' }).toEqual({ name: 'yueluo' }); // toEqual 可以判断对象属性是否相同
});
});
Truthiness
js
describe('truthiness', () => {
test('null', () => {
const n = null;
expect(n).toBeNull(); // 判断为 null
expect(n).toBeDefined(); // 判断是否已定义
expect(n).not.toBeUndefined(); // 判断不是未定义
expect(n).not.toBeTruthy(); // 判断不是 true
expect(n).toBeFalsy(); // 判断是 false
});
test('zero', () => {
const z = 0;
expect(z).not.toBeNull(); // 判断不是 null
expect(z).toBeDefined(); // 判断是否已定义
expect(z).not.toBeUndefined(); // 判断不是未定义
expect(z).not.toBeTruthy();// 判断不是 true
expect(z).toBeFalsy(); // 判断是 false
});
});
Numbers
js
describe('numbers', () => {
test('two plus two', () => {
const value = 2 + 2;
expect(value).toBeGreaterThan(3);
expect(value).toBeGreaterThanOrEqual(3.5);
expect(value).toBeLessThan(5);
expect(value).toBeLessThanOrEqual(4.5);
// toBe and toEqual are equivalent for numbers
expect(value).toBe(4);
expect(value).toEqual(4);
})
test('adding floating point numbers', () => {
const value = 0.1 + 0.2;
//expect(value).toBe(0.3); This won't work because of rounding error
expect(value).toBeCloseTo(0.3); // This works.
});
})
Strings
js
describe('strings', () => {
test('there is no I in team', () => {
expect('team').not.toMatch(/I/);
});
test('but there is a "stop" in Christoph', () => {
expect('Christoph').toMatch(/stop/);
});
})
Array and iterables
js
describe('arrays', () => {
const shoppingList = [
'diapers',
'kleenex',
'trash bags',
'paper towels',
'milk',
];
test('the shopping list has milk on it', () => {
expect(shoppingList).toContain('milk');
expect(shoppingList.length).toBe(5);
expect(new Set(shoppingList)).toContain('milk');
});
})
Exceptions
js
describe('exceptions', () => {
function compileAndroidCode() {
throw new Error('you are using the wrong JDK');
}
test('compiling android goes as expected', () => {
expect(() => compileAndroidCode()).toThrow();
expect(() => compileAndroidCode()).toThrow(Error);
// You can also use the exact error message or a regexp
expect(() => compileAndroidCode()).toThrow('you are using the wrong JDK');
expect(() => compileAndroidCode()).toThrow(/JDK/);
});
})
And More
This is just a taste. For a complete list of matchers, check out the reference docs.
Once you've learned about the matchers that are available, a good next step is to check out how Jest lets you test asynchronous code.
测试异步代码
新建 async.test.js 文件，并执行以下命令。
js
npx jest async.test.js --watch
回调函数形式
js
function getData (callback) {
setTimeout(() => {
callback({ author: 'heora' })
}, 1000)
}
// 错误示范：这种写法不会等待定时器结束
test('async fail', () => {
getData(data => {
expect(data).toEqual({ author: 'heora' })
})
})
// 正确做法
test('async success', (done) => {
getData(data => {
done();
expect(data).toEqual({ author: 'heora' })
})
})
Promise 形式
js
function getData () {
return new Promise((resolve, reject) => {
setTimeout(() => {
resolve({ author: 'heora' })
}, 1000)
})
}
test('async promise1', (done) => {
getData().then(data => {
done();
expect(data).toEqual({ author: 'heora' })
})
})
test('async promise2', () => {
return getData().then(data => {
expect(data).toEqual({ author: 'heora' })
})
})
test('async promise3', () => {
// return expect(getData()).rejects.toMatch('error');
return expect(getData()).resolves.toEqual({ author: 'heora' });
})
test('async promise4', async () => {
try {
const data = await getData();
expect(data).toEqual({ author: 'heora' })
} catch (error) {
expect(error).toMatch('error');
}
})
test('async promise5', async () => {
// await expect(getData()).rejects.toMatch('error');
await expect(getData()).resolves.toEqual({ author: 'heora' });
})
Mock
定时器
长时间处理
js
// 针对超长时间的异步函数
describe('timer: long', () => {
function getData () {
return new Promise((resolve, reject) => {
setTimeout(() => {
resolve({ author: 'heora' })
}, 10 * 1000)
})
}
// mock 定时器
jest.useFakeTimers();
test('timer mock', () => {
// 至少存在一次断言调用
expect.assertions(1);
getData().then(data => {
expect(data).toEqual({ author: 'heora' })
})
// 快进所有定时器到结束
jest.runAllTimers()
})
});
循环处理
js
describe('timer: loop', () => {
function getData () {
return new Promise((resolve, reject) => {
setTimeout(() => {
resolve({ author: 'heora' })
getData();
}, 10 * 1000)
})
}
// mock 定时器
jest.useFakeTimers();
test('timer mock', () => {
// 至少存在一次断言调用
expect.assertions(1);
getData().then(data => {
expect(data).toEqual({ author: 'heora' })
})
// 快进当前进行的定时器结束，不等待其它
jest.runOnlyPendingTimers()
})
});
快进指定时间
js
describe('timer: set time', () => {
function getData () {
return new Promise((resolve, reject) => {
setTimeout(() => {
resolve({ author: 'heora' })
}, 10 * 1000)
})
}
// mock 定时器
jest.useFakeTimers();
test('timer mock', () => {
// 至少存在一次断言调用
expect.assertions(1);
getData().then(data => {
expect(data).toEqual({ author: 'heora' })
})
jest.advanceTimersByTime(9 * 1000);
jest.advanceTimersByTime(1 * 1000);
})
});
函数
基本用法
js
function forEach (items, callback) {
for (let index = 0; index < items.length; index++) {
callback(items[index], index);
}
}
test('mock functions', () => {
const items = ['js', 'ts', 'nodejs'];
const mockFn = jest.fn((value, index) => {
return value + 1;
});
// 调用函数设置返回值会覆盖上面的实现
// mockFn.mockReturnValue(123);
// 调用函数设置第一个返回值
mockFn.mockReturnValueOnce(123);
forEach(items, mockFn);
console.log(mockFn.mock);
expect(mockFn.mock.calls.length).toBe(items.length);
expect(mockFn.mock.calls[0][0]).toBe('js');
expect(mockFn.mock.calls[0][1]).toBe(0);
})
模拟模块
例如使用 axios，不需要真实请求，可以提高测试速度。
js
// users.json
[
{
"author": "yueluo"
},
{
"author": "heora"
}
]
js
// user.js
import axios from "axios";
export const getAllUsers = () => {
return axios.get('/users.json').then(res => res.data);
}
js
// user.test.js
import axios from 'axios';
import { getAllUsers } from './user';
import users from './users.json';
jest.mock('axios');
test('fetch users', async () => {
const resp = { data: users };
axios.get.mockResolvedValue(resp);
const data = await getAllUsers();
expect(data).toEqual(users);
})
模拟实现
当函数内部存在大量计算，或者功能较多时，可以使用。
js
// foo.js
export default function () {
console.log('foo');
}
js
// foo.test.js
jest.mock('./foo');
import foo from "./foo";
foo.mockImplementation(() => 42);
test('mock implementations', () => {
expect(foo()).toBe(42);
});
模拟名称
js
const myMockFn = jest
.fn()
.mockReturnValue('default')
.mockImplementation(scalar => 42 + scalar)
.mockName('add42');
自定义匹配器
js
// The mock function was called at least once
expect(mockFunc).toHaveBeenCalled();
// The mock function was called at least once with the specified args
expect(mockFunc).toHaveBeenCalledWith(arg1, arg2);
// The last call to the mock function was called with the specified args
expect(mockFunc).toHaveBeenLastCalledWith(arg1, arg2);
// All calls and the name of the mock is written as a snapshot
expect(mockFunc).toMatchSnapshot();
更多用法可以点击这里查看。
钩子函数
可以在测试用例执行前后做一些通用的操作。
js
const data = {
author: 'yueluo'
}
let user = null;
beforeAll(() => {
console.log('before all')
})
afterAll(() => {
console.log('after all')
})
// 每个实例运行之前
beforeEach(() => {
user = Object.assign({}, data)
})
// 每个实例运行之后
afterEach(() => {
user = null
})
test('test 1', () => {
user.author = 'heora';
expect(user.author).toBe('heora')
})
test('test 2', () => {
expect(user.author).toBe('yueluo')
})
分组
describe 内部的 beforeEach 仅对当前内部的测试用例生效
js
describe('group', () => {
beforeEach(() => {
console.log('group before each')
})
afterEach(() => {
console.log('group after each')
})
test('test1', () => {
console.log('group test1')
})
test('test2', () => {
console.log('group test2')
})
})
DOM 测试
Jest 配合 jest-environment-jsdom 可以做到在 nodejs 环境中模拟 DOM API。
jsdom 不再默认内置于 jest v28 ，需要显式安装
js
pnpm i jest-environment-jsdom -D
js
/**
* @jest-environment jsdom
*/
function renderHtml () {
const div = document.createElement('div');
div.innerHTML = `
<h1>Hello World</h1>
`
document.body.appendChild(div);
}
test('dom testing', () => {
renderHtml();
expect(document.querySelector('h1').innerHTML).toBe('Hello World');
})
Vue 组件测试
js
pnpm i vue@2
js
/**
* @jest-environment jsdom
*/
import Vue from 'vue/dist/vue';
function renderVueComponent () {
document.body.innerHTML = `
<div id="app"></div>
`
new Vue({
template: `
<div id="app">
<h1>{{ message }}</h1>
</div>
`,
data: {
message: 'Hello World'
}
}).$mount('#app');
}
test('vue testing', () => {
renderVueComponent();
console.log(document.body.innerHTML)
expect(document.body.innerHTML).toMatch(/Hello World/)
})
快照测试
js
/**
* @jest-environment jsdom
*/
import Vue from 'vue/dist/vue';
function renderVueComponent () {
document.body.innerHTML = `
<div id="app"></div>
`
new Vue({
template: `
<div id="app">
<h1>{{ message }}</h1>
</div>
`,
data: {
message: 'Hello World'
}
}).$mount('#app');
}
test.only('Snapshot Testing', () => {
renderVueComponent();
// 首次运行时，会生成快照文件
// 下次运行测试会与快照文件进行比对，如果不一致测试失败
expect(document.body.innerHTML).toMatchSnapshot();
})
快照文件（__snapshots__/vue.test.js.snap）：
js
// Jest Snapshot v1, https://goo.gl/fbAQLP
exports[`Snapshot Testing 1`] = `
"
<div id=\\"app\\"><h1>Hello World</h1></div>
"
`;
如果模板确实有更改，我们可以更新快照。
js
npx jest vue.test.js --updateSnapshot