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Eslint rules for Jest

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eslint-plugin-jest

ESLint plugin for Jest

Actions Status

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 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.

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

This setting is detected automatically based off the version of the jest package installed in node_modules, but it can also be provided explicitly if desired:

{
  "settings": {
    "jest": {
      "version": 26
    }
  }
}

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).

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

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

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

RuleDescriptionConfigurationsFixable
consistent-test-itHave control over test and it usagesfixable
expect-expectEnforce assertion to be made in a test bodyrecommended
lowercase-nameEnforce lowercase test namesfixable
max-nested-describeEnforces a maximum depth to nested describe calls
no-alias-methodsDisallow alias methodsstylefixable
no-commented-out-testsDisallow commented out testsrecommended
no-conditional-expectPrevent calling expect conditionallyrecommended
no-deprecated-functionsDisallow use of deprecated functionsrecommendedfixable
no-disabled-testsDisallow disabled testsrecommended
no-done-callbackAvoid using a callback in asynchronous tests and hooksrecommendedsuggest
no-duplicate-hooksDisallow duplicate setup and teardown hooks
no-exportDisallow using exports in files containing testsrecommended
no-focused-testsDisallow focused testsrecommendedsuggest
no-hooksDisallow setup and teardown hooks
no-identical-titleDisallow identical titlesrecommended
no-ifDisallow conditional logic
no-interpolation-in-snapshotsDisallow string interpolation inside snapshotsrecommended
no-jasmine-globalsDisallow Jasmine globalsrecommendedfixable
no-jest-importDisallow importing Jestrecommended
no-large-snapshotsdisallow large snapshots
no-mocks-importDisallow manually importing from __mocks__recommended
no-restricted-matchersDisallow specific matchers & modifiers
no-standalone-expectDisallow using expect outside of it or test blocksrecommended
no-test-prefixesUse .only and .skip over f and xrecommendedfixable
no-test-return-statementDisallow explicitly returning from tests
prefer-called-withSuggest using toBeCalledWith() or toHaveBeenCalledWith()
prefer-expect-assertionsSuggest using expect.assertions() OR expect.hasAssertions()suggest
prefer-hooks-on-topSuggest having hooks before any test cases
prefer-spy-onSuggest using jest.spyOn()fixable
prefer-strict-equalSuggest using toStrictEqual()suggest
prefer-to-be-nullSuggest using toBeNull()stylefixable
prefer-to-be-undefinedSuggest using toBeUndefined()stylefixable
prefer-to-containSuggest using toContain()stylefixable
prefer-to-have-lengthSuggest using toHaveLength()stylefixable
prefer-todoSuggest using test.todofixable
require-to-throw-messageRequire a message for toThrow()
require-top-level-describeRequire test cases and hooks to be inside a describe block
valid-describeEnforce valid describe() callbackrecommended
valid-expectEnforce valid expect() usagerecommended
valid-expect-in-promiseEnforce having return statement when testing with promisesrecommended
valid-titleEnforce valid titlesrecommendedfixable

TypeScript Rules

In addition to the above rules, this plugin also includes a few advanced rules that are powered by type-checking information provided by TypeScript.

In order to use these rules, 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 its 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.

RuleDescriptionConfigurationsFixable
unbound-methodEnforces unbound methods are called with their expected scope

Credit

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

eslint-plugin-istanbul

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

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Popularity60/100
Quality81/100
Maintenance99/100