eslint-plugin-jest

ESLint plugin for Jest

yarn add --dev eslint eslint-plugin-jest

Note: If you installed ESLint globally then you must also install eslint-plugin-jest globally.

Add jest to the plugins section of your .eslintrc configuration file. You can omit the eslint-plugin- prefix:

{
  "plugins": ["jest"]
}

Then configure the rules you want to use under the rules section.

{
  "rules": {
    "jest/no-disabled-tests": "warn",
    "jest/no-focused-tests": "error",
    "jest/no-identical-title": "error",
    "jest/prefer-to-have-length": "warn",
    "jest/valid-expect": "error"
  }
}

You can also tell ESLint about the environment variables provided by Jest by doing:

{
  "env": {
    "jest/globals": true
  }
}

This is included in all configs shared by this plugin, so can be omitted if extending them.

You can tell this plugin about any global Jests you have aliased using the globalAliases setting:

{
  "settings": {
    "jest": {
      "globalAliases": {
        "describe": ["context"],
        "fdescribe": ["fcontext"],
        "xdescribe": ["xcontext"]
      }
    }
  }
}

You can tell this plugin to treat a different package as the source of Jest globals using the globalPackage setting:

{
  "settings": {
    "jest": {
      "globalPackage": "bun:test"
    }
  }
}

The rules provided by this plugin assume that the files they are checking are test-related. This means it's generally not suitable to include them in your top-level configuration as that applies to all files being linted which can include source files.

For .eslintrc configs you can use overrides to have ESLint apply additional rules to specific files:

{
  "extends": ["eslint:recommended"],
  "overrides": [
    {
      "files": ["test/**"],
      "plugins": ["jest"],
      "extends": ["plugin:jest/recommended"],
      "rules": { "jest/prefer-expect-assertions": "off" }
    }
  ],
  "rules": {
    "indent": ["error", 2]
  }
}

For eslint.config.js you can use files and ignores:

const jest = require('eslint-plugin-jest');

module.exports = [
  ...require('@eslint/js').configs.recommended,
  {
    files: ['test/**'],
    ...jest.configs['flat/recommended'],
    rules: {
      ...jest.configs['flat/recommended'].rules,
      'jest/prefer-expect-assertions': 'off',
    },
  },
  // you can also configure jest rules in other objects, so long as some of the `files` match
  {
    files: ['test/**'],
    rules: { 'jest/prefer-expect-assertions': 'off' },
  },
];

The behaviour of some rules (specifically no-deprecated-functions) change depending on the version of Jest being used.

By default, this plugin will attempt to determine to locate Jest using require.resolve, meaning it will start looking in the closest node_modules folder to the file being linted and work its way up.

Since we cache the automatically determined version, if you're linting sub-folders that have different versions of Jest, you may find that the wrong version of Jest is considered when linting. You can work around this by providing the Jest version explicitly in nested ESLint configs:

{
  "settings": {
    "jest": {
      "version": 27
    }
  }
}

To avoid hard-coding a number, you can also fetch it from the installed version of Jest if you use a JavaScript config file such as .eslintrc.js:

module.exports = {
  settings: {
    jest: {
      version: require('jest/package.json').version,
    },
  },
};

This plugin exports a recommended configuration that enforces good testing practices.

To enable this configuration with .eslintrc, use the extends property:

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

To enable this configuration with eslint.config.js, use jest.configs['flat/recommended']:

const jest = require('eslint-plugin-jest');

module.exports = [
  {
    files: [
      /* glob matching your test files */
    ],
    ...jest.configs['flat/recommended'],
  },
];

This plugin also exports a configuration named style, which adds some stylistic rules, such as prefer-to-be-null, which enforces usage of toBeNull over toBe(null).

To enable this configuration use the extends property in your .eslintrc config file:

{
  "extends": ["plugin:jest/style"]
}

To enable this configuration with eslint.config.js, use jest.configs['flat/style']:

const jest = require('eslint-plugin-jest');

module.exports = [
  {
    files: [
      /* glob matching your test files */
    ],
    ...jest.configs['flat/style'],
  },
];

If you want to enable all rules instead of only some you can do so by adding the all configuration to your .eslintrc config file:

{
  "extends": ["plugin:jest/all"]
}

To enable this configuration with eslint.config.js, use jest.configs['flat/all']:

const jest = require('eslint-plugin-jest');

module.exports = [
  {
    files: [
      /* glob matching your test files */
    ],
    ...jest.configs['flat/all'],
  },
];

While the recommended and style configurations only change in major versions the all configuration may change in any release and is thus unsuited for installations requiring long-term consistency.

💼 Configurations enabled in.
⚠️ Configurations set to warn in.
✅ Set in the recommended configuration.
🎨 Set in the style configuration.
🔧 Automatically fixable by the --fix CLI option.
💡 Manually fixable by editor suggestions.

In order to use the rules powered by TypeScript type-checking, you must be using @typescript-eslint/parser & adjust your eslint config as outlined here.

Note that unlike the type-checking rules in @typescript-eslint/eslint-plugin, the rules here will fallback to doing nothing if type information is not available, meaning it's safe to include them in shared configs that could be used on JavaScript and TypeScript projects.

Also note that unbound-method depends on @typescript-eslint/eslint-plugin, as it extends the original unbound-method rule from that plugin.

• eslint-plugin-mocha
• eslint-plugin-jasmine

This is a sister plugin to eslint-plugin-jest that provides support for the matchers provided by jest-extended.

https://github.com/jest-community/eslint-plugin-jest-extended

This project aims to provide formatting rules (auto-fixable where possible) to ensure consistency and readability in jest test suites.

https://github.com/dangreenisrael/eslint-plugin-jest-formatting

A set of rules to enforce good practices for Istanbul, one of the code coverage tools used by Jest.

https://github.com/istanbuljs/eslint-plugin-istanbul