【自动化测试】Jest体验之旅

喜欢ヅ旅行 2024-03-22 22:48 92阅读 0赞

**目录**

简介

快速体验

配置文件

Jest CLI 选项

\--watchAll

\--watch

使用 ES6 模块

--------------------

### 简介 ###

Jest 是 Facebook 出品的一个 JavaScript 开源测试框架。相对其他测试框架，其一大特点就是就是内置了常用的测试工具，比如零配置、自带断言、测试覆盖率工具等功能，实现了开箱即用。

Jest 适用但不局限于使用以下技术的项目：Babel,、TypeScript、 Node、 React、Angular、Vue 等。

Jest 主要特点：

*  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 等常见前端框架的自动测试。
 *  此外， Jest 的测试用例是并行执行的，而且只执行发生改变的文件所对应的测试，提升了测试速度。
 *  测试覆盖率
 *  Mock 模拟

### 快速体验 ###

用你喜欢的软件包管理工具来安装 Jest：

npm install --save-dev jest

给一个假定的函数写测试，这个函数的功能是两数相加。首先创建 sum.js 文件：

function sum(a, b) {
      return a + b;
    }
    module.exports = sum;

接下来，创建名为 sum.test.js 的文件。这个文件包含了实际测试内容：

const sum = require('./sum');
    
    test('adds 1 + 2 to equal 3', () => {
      expect(sum(1, 2)).toBe(3);
    });

将如下代码添加到 package.json 中：

{
      "scripts": {
        "test": "jest"
      }
    }

> jest 命令会运行项目中所有以 .test.js 结尾的文件

运行测试命令：

npm run test

![image.png][]

### 配置文件 ###

Jest 将根据项目提出一系列问题，并且将创建一个基础配置文件。文件中的每一项都配有简短的说明：

npx jest --init

详细配置信息参考：[jestjs.io/docs/zh-Han…][jestjs.io_docs_zh-Han]

// jest.config.js
    /*
     * For a detailed explanation regarding each configuration property, visit:
     * https://jestjs.io/docs/en/configuration.html
     */
    
    module.exports = {
      // 自动 mock 所有导入的外部模块
      // automock: false,
    
      // 在指定次数失败后停止运行测试
      // bail: 0,
    
      // The directory where Jest should store its cached dependency information
      // cacheDirectory: "/private/var/folders/5h/_98rffpj1z95b_0dm76lvzm40000gn/T/jest_dx",
    
      // 在每个测试之间自动清除 mock 调用和实例
      clearMocks: true,
    
      // 是否收集测试覆盖率信息
      // collectCoverage: false,
    
      // 一个 glob 模式数组，指示应该为其收集覆盖率信息的一组文件
      // collectCoverageFrom: undefined,
    
      // 测试覆盖率报错文件输出的目录
      coverageDirectory: "coverage",
    
      // 忽略测试覆盖率统计
      // coveragePathIgnorePatterns: [
      //   "/node_modules/"
      // ],
    
      // 指示应该使用哪个提供程序检测代码的覆盖率，默认是 babel，可选 v8，但是 v8 不太稳定，建议 Node 14 以上版本使用
      // 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,
    
      // 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",
      //   "json",
      //   "jsx",
      //   "ts",
      //   "tsx",
      //   "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 between 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 between 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: "jest-environment-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: "jasmine2",
    
      // This option sets the URL for the jsdom environment. It is reflected in properties such as location.href
      // testURL: "http://localhost",
    
      // Setting this value to "fake" allows the use of fake timers for functions such as "setTimeout"
      // timers: "real",
    
      // 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 CLI 选项 ###

参考：[jestjs.io/zh-Hans/doc…][jestjs.io_zh-Hans_doc]

#### \--watchAll ####

监视文件的更改并在任何更改时重新运行所有测试。

jest --watchAll

![image.png][image.png 1]

#### \--watch ####

> 该模式需要 Git 支持。

监视 Git 仓库中的文件更改，并重新运行与已更改的文件相关的测试。

jest --watch

### 使用 ES6 模块 ###

需要使用 [Babel][]，安装所需的依赖。

npm install --save-dev babel-jest @babel/core @babel/preset-env

在工程的根目录下创建一个babel.config.js文件用于配置与你当前Node版本兼容的Babel：

module.exports = {
        presets: [["@babel/preset-env", { targets: { node: "current" } }]],
    };

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。

Jest 结合 Babel 的运行原理：运行测试之前，结合 Babel，先把你的代码做一次转化，模块被转换为了 CommonJS，运行转换之后的测试用例代码。

过程：

*  npm run jest
 *  jest
 *  babel-jest
 *  babel-core
 *  babel 配置文件
 *  转换为 ES5
 *  执行转换之后的测试代码

--------------------

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[image.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/14/f462dd903ae74b3e8785dc600cdad228.png
[jestjs.io_docs_zh-Han]: https://link.juejin.cn?target=https%3A%2F%2Fjestjs.io%2Fdocs%2Fzh-Hans%2Fconfiguration%25E3%2580%2582
[jestjs.io_zh-Hans_doc]: https://link.juejin.cn?target=https%3A%2F%2Fjestjs.io%2Fzh-Hans%2Fdocs%2Fcli
[image.png 1]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/14/fe20494b2d494321a2e64d89720a860e.png
[Babel]: https://link.juejin.cn?target=https%3A%2F%2Fbabeljs.io%2F
[c1653dd19f35495583cef3678b57b6b0.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/14/e96724fe2dbd42c58f5e324a9f307bc3.png
[775632765b6744fbbecbd8fdd097d1ab.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/14/144cce88d8a845db810f17d1328af4ae.png