为项目安装并配置Jest单元测试环境
分步指南
传送门:Jest - 快速入门
1. 安装jest:
npm i jest ts-jest @types/jest -D
2. 初始化:
npx jest --init
按照图中所示选择
tip:
- no;不使用ts,使用jest.config.js作为jest的配置文件;
- jsdom;使用jsdom作为测试环境(jsdom:一个类似浏览器的环境,项目是运行在浏览器的,需要在浏览器dom环境下测试);
- yes;是否添加测试报告;
- babel;使用babel提供的测试报告(官网说明v8仍处于试验阶段,需node14以上使用,效果未知,不稳定,因此选用babel);
3. 安装jsdom环境:
- jest 28及以上版本不再内置jsdom插件,需要单独安装
- 安装官方eslint插件:
npm i jest-environment-jsdom eslint-plugin-jest eslint-import-resolver-typescript jest-canvas-mock -D
4. 创建test目录
在项目根目录下创建test目录,然后在test下创建__mocks和__tests__目录,创建.eslintrc.js和tsconfig.json文件
附:配置示例
jest.config.js
/*
* For a detailed explanation regarding each configuration property, visit:
* https://jestjs.io/docs/configuration
*/const{ pathsToModuleNameMapper }=require('ts-jest');const{ compilerOptions }=require('./tsconfig.json');
module.exports ={// A preset that is used as a base for Jest's configurationpreset:'ts-jest',// The test environment that will be used for testingtestEnvironment:'jsdom',// The paths to modules that run some code to configure or set up the testing environment before each testsetupFiles:['jest-canvas-mock'],// Automatically clear mock calls, instances, contexts and results before every testclearMocks:true,// Indicates whether the coverage information should be collected while executing the testcollectCoverage:true,// The directory where Jest should output its coverage filescoverageDirectory:'test/coverage',// The root directory that Jest should scan for tests and modules within// rootDir: undefined,// rootDir: __dirname,// An array of file extensions your modules usemoduleFileExtensions:['ts','js'],// A map from regular expressions to module names or to arrays of module names that allow to stub out resources with a single modulemoduleNameMapper:pathsToModuleNameMapper(compilerOptions.paths,{prefix:'<rootDir>/',}),// The glob patterns Jest uses to detect test filestestMatch:['<rootDir>/test/__tests__/**/*.test.ts'],// A map from regular expressions to paths to transformerstransform:{'^.+\\.ts$':'ts-jest',},};
*配置测试用例的eslint规则
/test/.eslintrc.js
module.exports ={extends:['../.eslintrc.js'],settings:{'import/resolver':{typescript:{alwaysTryTypes:true,// always try to resolve types under `<root>@types` directory even it doesn't contain any source code, like `@types/unist`// Choose from one of the "project" configs below or omit to use <root>/tsconfig.json by default// use <root>/path/to/folder/tsconfig.jsonproject:'tsconfig.json',},},},plugins:['jest'],overrides:[// unit-tests{files:['**/__tests__/**'],rules:{'jest/no-disabled-tests':'warn','jest/no-focused-tests':'error','jest/no-identical-title':'error','jest/prefer-to-have-length':'warn','jest/valid-expect':'error',},},],};
*代码覆盖率报告无需加入git版本管理,将
test/coverage
目录追加至
.gitignore
...
# Unit test / coverage reports
test/coverage
中配置路径别名*tsconfig.json
5. 愉快地开始单元测试:
在
test/__test__
目录下新增自己模块的单元测试目录及文件,开始单元测试代码编写
文件命名规范:
*.test.ts
6. 总结 - 踩坑记录:
- 默认preset为
babel-jest
,由于Babel
对Typescript
的支持是通过代码转换(Transpilation)实现的,而 Jest 在运行时并不会对你的测试用例做类型检查。 因此建议安装ts-jest来开启此功能 - 主要是在配置
tsconfig.json
路径别名时花费了大量时间,处理ts的报错以及eslint的报错问题; - 以上配置的路径别名只需在
tsconfig.json
一处配置,随处可用,包括ts、eslint、jest都能读取同一个别名配置; - 另外对于webpack的别名配置,网上也有读取tsconfig配置的方案;
版权归原作者 __Simon 所有, 如有侵权,请联系我们删除。