解决jest处理es模块

问题场景

项目使用jest进行测试时, 当引入外部库是es模块时, jest无法处理导致报错.

Test suite failed to runJest encountered an unexpected tokenThis usually means that you are trying to import a file which Jest cannot parse, e.g. it's not plain JavaScript.By default, if Jest sees a Babel config, it will use that to transform your files, ignoring "node_modules".Here's what you can do:• To have some of your "node_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config.• If you need a custom transformation specify a "transform" option in your config.• If you simply want to mock your non-JS modules (e.g. binary assets) you can stub them out with the "moduleNameMapper" config option.Details:/home/xueyou/workspace/projects/node_modules/lodash-es/lodash.js:10import * as lodash from 'lodash-es'SyntaxError: Unexpected token *

解决方法

查阅issues发现, 目前jest不支持em模块, 只有通过babel去处理了

1. 安装依赖

   yarn add --dev babel-jest @babel/core @babel/preset-env babel-plugin-transform-es2015-modules-commonjs

2. 配置babel.config.js

   module.exports = {presets: [["@babel/preset-env",{targets: {node: "current"}}]],plugins: ["transform-es2015-modules-commonjs"]
   };
   

3. 配置jest.config.js

   module.exports = {preset: "ts-jest",testMatch: ["<rootDir>/tests/**/*.(spec|test).ts?(x)"],transform: {// 将.js后缀的文件使用babel-jest处理"^.+\\.js$": "babel-jest","^.+\\.(ts|tsx)$": "ts-jest"},// 下面非要从重要, 将不忽略 lodash-es, other-es-lib 这些es库, 从而使babel-jest去处理它们transformIgnorePatterns: ["<rootDir>/node_modules/(?!(lodash-es|other-es-lib))"]
   };
   

   脚注

   • Unexpected import inside nodejs module
   • Unexpected Token Import for ES6 modules