Jest 是否支持 ES6 导入/导出? [英] Does Jest support ES6 import/export?

问题描述

如果我从 ES6 使用 import/export 那么我所有的 Jest 测试都会失败并显示错误:

If I use import/export from ES6 then all my Jest tests fail with error:

意外的保留字

我将我的测试对象转换为使用旧式 IIFE 语法突然间我的测试通过了.或者，采用更简单的测试用例:

I convert my object under test to use old school IIFE syntax and suddenly my tests pass. Or, take an even simpler test case:

   var Validation = require('../src/components/validation/validation'); // PASS
   //import * as Validation from '../src/components/validation/validation' // FAIL

同样的错误.显然这里的导入/导出有问题.仅仅为了让我的测试框架满意而使用 ES5 语法重写我的代码对我来说是不切实际的.

Same error. Obviously there's a problem with import/export here. It's not practical for me to rewrite my code using ES5 syntax just to make my test framework happy.

我有 babel-jest.我尝试了来自 GitHub 问题的各种建议.到目前为止还不行.

I have babel-jest. I tried various suggestions from GitHub issues. It is no go so far.

 "scripts": {
    "start": "webpack-dev-server",
    "test": "jest"
  },
      "jest": {
        "testPathDirs": [
          "__tests__"
        ],
        "testPathIgnorePatterns": [
          "/node_modules/"
        ],
        "testFileExtensions": ["es6", "js"],
        "moduleFileExtensions": ["js", "json", "es6"]
      },

文件babelrc

{
  "presets": ["es2015", "react"],
  "plugins": ["transform-decorators-legacy"]
}

有没有办法解决这个问题?

Is there a fix for this?

推荐答案

UPDATE 2020 - ECMAScript 模块 (ESM) 的原生支持

---

根据这个问题，jest 有对 ESM 的原生支持@25.4.0.这样你就不必再使用 babel 了.在撰写此答案时 (05/2020)，要激活您需要做三件简单的事情:

UPDATE 2020 - native support of ECMAScript modules (ESM)

---

According to this issue, there is native support of ESM from jest@25.4.0. So you won't have to use babel anymore. At the time of writing this answer (05/2020), to activate that you need to do three simple things:

• 确保您不会通过在配置文件中设置 transform: {} 来转换 import 语句
• 运行node@^12.16.0 ||>=13.2.0 带有 --experimental-vm-modules 标志
• 使用 jest-environment-node 或 jest-environment-jsdom-sixteen 运行您的测试.

• Make sure you don't transform away import statements by setting transform: {} in config file
• Run node@^12.16.0 || >=13.2.0 with --experimental-vm-modules flag
• Run your test with jest-environment-node or jest-environment-jsdom-sixteen.

所以你的 Jest 配置文件应该至少包含以下内容:

So your Jest configuration file should contain at least this:

export default {
    testEnvironment: 'jest-environment-node',
    transform: {}
    ...
};

并且要设置 --experimental-vm-modules 标志，您必须按如下方式运行 Jest:

And to set --experimental-vm-modules flag, you will have to run Jest as follows:

node --experimental-vm-modules node_modules/jest/bin/jest.js

另请注意，在 Github 问题中，此方法尚不支持 jest 对象.所以你可能需要手动导入:

Also note in the Github issue that this approach does not yet support the jest object. So you may need to import it manually:

import {jest} from '@jest/globals'

(我希望这会在未来改变)

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