eslint-plugin-jest

ESLint plugin for Jest

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

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

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