在Jest测试中使用命名的导入内容导入"constants" [英] Importing `constants` in Jest tests with named imports

问题描述

我的项目中有一个config和constants文件夹.位于src\config\test.ts& src\constants\index.js.

I have a config and constants folder in my project. Located in src\config\test.ts & src\constants\index.js respectively.

我将Jest设置为使用moduleNameMapper如下，因此我可以执行import config from 'config'和import { SOME_CONST } from 'constants'

I've setup Jest to use moduleNameMapper as below so I can just do import config from 'config' and import { SOME_CONST } from 'constants'

"moduleNameMapper": {
  "config$": "<rootDir>/src/config/test.js",
  "constants$": "<rootDir>/src/constants/index.js"
}

但是，在我的测试中，任何使用import { SOME_CONST } from 'constants'的文件始终会为SOME_CONST获得undefined值，而我们默认从config导出的文件都可以正常工作.

However, in my tests any files which use import { SOME_CONST } from 'constants' always get an undefined value for SOME_CONST whereas any which us the default export from config work fine.

这是一个已知问题吗?我在这里做错什么了吗?似乎无法将其固定下来.

Is this a known issue? Am I doing something wrong here? can't seem to pin it down.

推荐答案

我遇到了与您相同的问题，但最终发现了这个此评论对我有用，并说要放入您的测试文件:

I was having the same issue as you, but I eventually found this github issue that addresses it. It looks like constants is a core module and therefore evaluated before jest's module mapping. I found this comment which worked for me and says to put this in your test file:

jest.mock('constants', () => require('path/to/your/constants'))

一种替代方法是执行@dougajmcdonald在他的评论中建议的操作，然后从constants重命名您的webpack别名去别的东西，例如app-constants.

An alternative is to do what @dougajmcdonald suggested in his comment above, and rename your webpack alias from constants to something else, e.g. app-constants.

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