# eslint-plugin-jest

ESLint plugin for Jest

[![Actions Status](https://github.com/jest-community/eslint-plugin-jest/actions/workflows/nodejs.yml/badge.svg?branch=main)](https://github.com/jest-community/eslint-plugin-jest/actions) ## Installation ```bash 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: ```json { "plugins": ["jest"] } ``` Then configure the rules you want to use under the rules section. ```json { "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: ```json { "env": { "jest/globals": true } } ``` This is included in all configs shared by this plugin, so can be omitted if extending them. ### Jest `version` setting 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: ```json { "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`: ```js module.exports = { settings: { jest: { version: require('jest/package.json').version, }, }, }; ``` ## 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: ```json { "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: ```json { "extends": ["plugin:jest/style"] } ``` See [ESLint documentation](https://eslint.org/docs/user-guide/configuring/configuration-files#extending-configuration-files) 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: ```json { "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 | Configurations | Fixable | | ---------------------------------------------------------------------------- | ------------------------------------------------------------------- | ---------------- | ------------ | | [consistent-test-it](docs/rules/consistent-test-it.md) | Have control over `test` and `it` usages | | ![fixable][] | | [expect-expect](docs/rules/expect-expect.md) | Enforce assertion to be made in a test body | ![recommended][] | | | [max-nested-describe](docs/rules/max-nested-describe.md) | Enforces a maximum depth to nested describe calls | | | | [no-alias-methods](docs/rules/no-alias-methods.md) | Disallow alias methods | ![style][] | ![fixable][] | | [no-commented-out-tests](docs/rules/no-commented-out-tests.md) | Disallow commented out tests | ![recommended][] | | | [no-conditional-expect](docs/rules/no-conditional-expect.md) | Prevent calling `expect` conditionally | ![recommended][] | | | [no-deprecated-functions](docs/rules/no-deprecated-functions.md) | Disallow use of deprecated functions | ![recommended][] | ![fixable][] | | [no-disabled-tests](docs/rules/no-disabled-tests.md) | Disallow disabled tests | ![recommended][] | | | [no-done-callback](docs/rules/no-done-callback.md) | Avoid using a callback in asynchronous tests and hooks | ![recommended][] | ![suggest][] | | [no-duplicate-hooks](docs/rules/no-duplicate-hooks.md) | Disallow duplicate setup and teardown hooks | | | | [no-export](docs/rules/no-export.md) | Disallow using `exports` in files containing tests | ![recommended][] | | | [no-focused-tests](docs/rules/no-focused-tests.md) | Disallow focused tests | ![recommended][] | ![suggest][] | | [no-hooks](docs/rules/no-hooks.md) | Disallow setup and teardown hooks | | | | [no-identical-title](docs/rules/no-identical-title.md) | Disallow identical titles | ![recommended][] | | | [no-if](docs/rules/no-if.md) | Disallow conditional logic | | | | [no-interpolation-in-snapshots](docs/rules/no-interpolation-in-snapshots.md) | Disallow string interpolation inside snapshots | ![recommended][] | | | [no-jasmine-globals](docs/rules/no-jasmine-globals.md) | Disallow Jasmine globals | ![recommended][] | ![fixable][] | | [no-jest-import](docs/rules/no-jest-import.md) | Disallow importing Jest | ![recommended][] | | | [no-large-snapshots](docs/rules/no-large-snapshots.md) | disallow large snapshots | | | | [no-mocks-import](docs/rules/no-mocks-import.md) | Disallow manually importing from `__mocks__` | ![recommended][] | | | [no-restricted-matchers](docs/rules/no-restricted-matchers.md) | Disallow specific matchers & modifiers | | | | [no-standalone-expect](docs/rules/no-standalone-expect.md) | Disallow using `expect` outside of `it` or `test` blocks | ![recommended][] | | | [no-test-prefixes](docs/rules/no-test-prefixes.md) | Use `.only` and `.skip` over `f` and `x` | ![recommended][] | ![fixable][] | | [no-test-return-statement](docs/rules/no-test-return-statement.md) | Disallow explicitly returning from tests | | | | [prefer-called-with](docs/rules/prefer-called-with.md) | Suggest using `toBeCalledWith()` or `toHaveBeenCalledWith()` | | | | [prefer-comparison-matcher](docs/rules/prefer-comparison-matcher.md) | Suggest using the built-in comparison matchers | | ![fixable][] | | [prefer-equality-matcher](docs/rules/prefer-equality-matcher.md) | Suggest using the built-in equality matchers | | ![suggest][] | | [prefer-expect-assertions](docs/rules/prefer-expect-assertions.md) | Suggest using `expect.assertions()` OR `expect.hasAssertions()` | | ![suggest][] | | [prefer-expect-resolves](docs/rules/prefer-expect-resolves.md) | Prefer `await expect(...).resolves` over `expect(await ...)` syntax | | ![fixable][] | | [prefer-hooks-on-top](docs/rules/prefer-hooks-on-top.md) | Suggest having hooks before any test cases | | | | [prefer-lowercase-title](docs/rules/prefer-lowercase-title.md) | Enforce lowercase test names | | ![fixable][] | | [prefer-spy-on](docs/rules/prefer-spy-on.md) | Suggest using `jest.spyOn()` | | ![fixable][] | | [prefer-strict-equal](docs/rules/prefer-strict-equal.md) | Suggest using `toStrictEqual()` | | ![suggest][] | | [prefer-to-be](docs/rules/prefer-to-be.md) | Suggest using `toBe()` for primitive literals | ![style][] | ![fixable][] | | [prefer-to-contain](docs/rules/prefer-to-contain.md) | Suggest using `toContain()` | ![style][] | ![fixable][] | | [prefer-to-have-length](docs/rules/prefer-to-have-length.md) | Suggest using `toHaveLength()` | ![style][] | ![fixable][] | | [prefer-todo](docs/rules/prefer-todo.md) | Suggest using `test.todo` | | ![fixable][] | | [require-hook](docs/rules/require-hook.md) | Require setup and teardown code to be within a hook | | | | [require-to-throw-message](docs/rules/require-to-throw-message.md) | Require a message for `toThrow()` | | | | [require-top-level-describe](docs/rules/require-top-level-describe.md) | Require test cases and hooks to be inside a `describe` block | | | | [valid-describe-callback](docs/rules/valid-describe-callback.md) | Enforce valid `describe()` callback | ![recommended][] | | | [valid-expect](docs/rules/valid-expect.md) | Enforce valid `expect()` usage | ![recommended][] | | | [valid-expect-in-promise](docs/rules/valid-expect-in-promise.md) | Ensure promises that have expectations in their chain are valid | ![recommended][] | | | [valid-title](docs/rules/valid-title.md) | Enforce valid titles | ![recommended][] | ![fixable][] | ## 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](https://github.com/typescript-eslint/typescript-eslint/blob/master/docs/getting-started/linting/TYPED_LINTING.md) 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. | Rule | Description | Configurations | Fixable | | ---------------------------------------------- | ------------------------------------------------------------- | -------------- | ------- | | [unbound-method](docs/rules/unbound-method.md) | Enforces unbound methods are called with their expected scope | | | ## Credit - [eslint-plugin-mocha](https://github.com/lo1tuma/eslint-plugin-mocha) - [eslint-plugin-jasmine](https://github.com/tlvince/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 ### 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 [recommended]: https://img.shields.io/badge/-recommended-lightgrey.svg [suggest]: https://img.shields.io/badge/-suggest-yellow.svg [fixable]: https://img.shields.io/badge/-fixable-green.svg [style]: https://img.shields.io/badge/-style-blue.svg [`no-deprecated-functions`]: docs/rules/no-deprecated-functions.md