eslint 在检查 Jest 测试文件时抛出 `no-undef` 错误

Question

I'm using Jest to write some specs and ESLint to lint the styling.

For my foo.spec.js tests, eslint keeps throwing the following errors. It seems to think that jest , beforeEach , afterEach , etc... are not defined in that file.

   11:1   error  'beforeEach' is not defined  no-undef
   12:3   error  'jest' is not defined        no-undef
   14:13  error  'jest' is not defined        no-undef
   18:1   error  'afterEach' is not defined   no-undef
   20:1   error  'describe' is not defined    no-undef
   21:3   error  'it' is not defined          no-undef
   25:5   error  'expect' is not defined      no-undef
   28:5   error  'expect' is not defined      no-undef
   31:5   error  'expect' is not defined      no-undef
   34:3   error  'it' is not defined          no-undef
   38:5   error  'expect' is not defined      no-undef
   41:5   error  'jest' is not defined        no-undef
   42:5   error  'expect' is not defined      no-undef
   43:5   error  'expect' is not defined      no-undef
   46:3   error  'it' is not defined          no-undef
   54:5   error  'expect' is not defined      no-undef
   58:5   error  'jest' is not defined        no-undef

I believe those are included by jest automatically and so they don't need to be explicitly imported in my spec files. In fact the only thing I import via my jest.setup.js file is

import "react-testing-library/cleanup-after-each";
import "jest-dom/extend-expect";

Is there a way to eliminate these errors without having to disable eslint rules at the top of each individual file or inline?

Thanks!

Answer 1

Please, add the following to your .eslintrc file:

{
  "overrides": [
    {
      "files": [
        "**/*.spec.js",
        "**/*.spec.jsx"
      ],
      "env": {
        "jest": true
      }
    }
  ]
}

Answer 2

You do not need to add this override option and specify in which files jest should be available. Adding only env field should be enough.

.eslintrc.js :

module.exports = {
  env: {
    jest: true
  },
//...
}

Answer 3

Had a similar problem with eslint throwing no-undef errors for my jest setup.js file with some jest.mocks in it.

Ended up fixing it by using the ESLint plugin for Jest .

After installing the plugin as a dev dependency, I merged the following into my .eslintrc config file per instructions from the plugin readme.

{
  "extends": ["plugin:jest/recommended"],
  "plugins": ["jest"]
}

Then the no-undef errors are gone.

Answer 4

As I am using a StandardJS Linter none of the suggested solution worked for me. Instead, I had to define a global for "it" within my standard-config.

Eg in package.json :

...
  "standard": {
    "parser": "babel-eslint",
    "globals": [
      "afterAll",
      "beforeAll",
      "afterEach",
      "jasmine",
      "describe",
      "test",
      "jest",
      "expect",
      "it"
    ]
 }
...

Answer 5

The environment can also be applied to individual files (without modifying configuration files).

For example, use this comment at the top of the file:

/* eslint-env jest */

This can be useful when there are some files (eg jest.setup.js ), that access jest. and are outside the regular test folders.