解决jest处理es模块

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 run

    Jest encountered an unexpected token

    This 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:10

import * 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