Installation

$ yarn add --dev eslint eslint-plugin-jest

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

Usage

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 whitelist the environment variables provided by Jest by doing:

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

Shareable configurations

Recommended

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

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

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

Style

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). All rules included are:

• prefer-to-be-null
• prefer-to-be-undefined
• prefer-to-contain
• prefer-to-have-length

See ESLint documentation for more information about extending configuration files.

All

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"]
}

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.

Rules

| Rule | Description | Recommended | Fixable | | ---------------------------- | ----------------------------------------------------------------- | ---------------- | ------------------- | | consistent-test-it | Enforce consistent test or it keyword | | | | expect-expect | Enforce assertion to be made in a test body | | | | lowercase-name | Disallow capitalized test names | | | | no-alias-methods | Disallow alias methods | | | | no-disabled-tests | Disallow disabled tests | | | | no-commented-out-tests | Disallow commented out tests | | | | no-empty-title | Disallow empty titles | | | | no-focused-tests | Disallow focused tests | | | | no-hooks | Disallow setup and teardown hooks | | | | no-identical-title | Disallow identical titles | | | | no-jasmine-globals | Disallow Jasmine globals | | | | no-jest-import | Disallow importing jest | | | | no-mocks-import | Disallow manually importing from __mocks__ | | | | no-large-snapshots | Disallow large snapshots | | | | no-test-callback | Using a callback in asynchronous tests | | | | no-test-prefixes | Disallow using f & x prefixes to define focused/skipped tests | | | | no-test-return-statement | Disallow explicitly returning from tests | | | | no-truthy-falsy | Disallow using toBeTruthy() & toBeFalsy() | | | | prefer-expect-assertions | Suggest using expect.assertions() OR expect.hasAssertions() | | | | prefer-spy-on | Suggest using jest.spyOn() | | | | prefer-strict-equal | Suggest using toStrictEqual() | | | | prefer-to-be-null | Suggest using toBeNull() | | | | prefer-to-be-undefined | Suggest using toBeUndefined() | | | | prefer-to-contain | Suggest using toContain() | | | | prefer-to-have-length | Suggest using toHaveLength() | | | | prefer-inline-snapshots | Suggest using toMatchInlineSnapshot() | | | | require-tothrow-message | Require that toThrow() and toThrowError includes a message | | | | valid-describe | Enforce valid describe() callback | | | | valid-expect-in-promise | Enforce having return statement when testing with promises | | | | valid-expect | Enforce valid expect() usage | | | | prefer-todo | Suggest using test.todo() | | | | prefer-called-with | Suggest using toBeCalledWith() OR toHaveBeenCalledWith() | | |

Credit

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

Related Projects

eslint-plugin-jest-formatting

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