eslint-plugin-cypress

What is eslint-plugin-cypress?

The eslint-plugin-cypress npm package provides a set of linting rules specific to Cypress, an end-to-end testing framework. These rules help developers adhere to best practices and avoid common mistakes when writing Cypress tests.

What are eslint-plugin-cypress's main functionalities?

Enforcing Assertions

Ensures that assertions are made in test cases to prevent tests that mistakenly pass without asserting any conditions.

expect(something).to.be.true;

Disallowing Assignment in Conditional Expressions

Prevents the use of assignment operators in conditional expressions, which can lead to tests that pass incorrectly due to an assignment rather than a proper comparison.

if (user = getUser()) { /* ... */ }

Disallowing Unnecessary Waiting

Discourages the use of arbitrary wait times in tests, promoting the use of Cypress's built-in waiting mechanisms that are more reliable and efficient.

cy.wait(5000);

Other packages similar to eslint-plugin-cypress

eslint-plugin-jest

This package provides linting rules for Jest, another popular testing framework. It is similar to eslint-plugin-cypress in that it offers a set of rules tailored to the specific testing framework to encourage best practices.

eslint-plugin-mocha

Similar to eslint-plugin-cypress, this package offers linting rules for Mocha, a test framework for Node.js and the browser. It helps maintain code quality and adherence to Mocha-specific conventions.

eslint-plugin-testing-library

This package is designed for linting code that uses the Testing Library family of utilities. It provides rules that help enforce best practices when writing tests with Testing Library, similar to how eslint-plugin-cypress does for Cypress tests.

README

Cypress ESLint Plugin

An ESLint plugin for your Cypress tests.

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

Installation

Prerequisites: ESLint v7, v8 or v9. This plugin supports the use of Flat config files with ESLint 8.57.0 and above.

npm install eslint-plugin-cypress --save-dev

or

yarn add eslint-plugin-cypress --dev

Usage

If you are using ESLint v7 or v8, then add an .eslintrc.json file to the root directory of your Cypress project with the contents shown below. You can continue to use this format with ESLint v9 if you set the ESLINT_USE_FLAT_CONFIG environment variable to false (see ESLint v9 > Configuration Files (Deprecated).

ESLint v9 uses a Flat config file format with filename eslint.config.*js by default. Please refer to additional Flat config installation and configuration details. (You may also use this with ESLint 8.57.0.)

{
  "plugins": [
    "cypress"
  ]
}

You can add rules:

{
  "rules": {
    "cypress/no-assigning-return-values": "error",
    "cypress/no-unnecessary-waiting": "error",
    "cypress/assertion-before-screenshot": "warn",
    "cypress/no-force": "warn",
    "cypress/no-async-tests": "error",
    "cypress/no-async-before": "error",
    "cypress/no-pause": "error"
  }
}

You can allow certain globals provided by Cypress:

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

Recommended configuration

Use the recommended configuration and you can forego configuring plugins, rules, and env individually. See below for which rules are included.

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

Disable rules

You can disable specific rules per file, for a portion of a file, or for a single line.

Disable the cypress/no-unnecessary-waiting rule for the entire file by placing this at the start of the file:

/* eslint-disable cypress/no-unnecessary-waiting */

Disable the cypress/no-unnecessary-waiting rule for only a portion of the file:

it('waits for a second', () => {
  ...
  /* eslint-disable cypress/no-unnecessary-waiting */
  cy.wait(1000)
  /* eslint-enable cypress/no-unnecessary-waiting */
  ...
})

Disable the cypress/no-unnecessary-waiting rule for a specific line:

it('waits for a second', () => {
  ...
  cy.wait(1000) // eslint-disable-line cypress/no-unnecessary-waiting
  ...
})

You can also disable a rule for the next line:

it('waits for a second', () => {
  ...
  // eslint-disable-next-line cypress/no-unnecessary-waiting
  cy.wait(1000)
  ...
})

For more, see the ESLint rules documentation.

Rules

These rules enforce some of the best practices recommended for using Cypress.

💼 Configurations enabled in.
✅ Set in the recommended configuration.

Name	Description	💼
assertion-before-screenshot	require screenshots to be preceded by an assertion
no-assigning-return-values	disallow assigning return values of cy calls	✅
no-async-before	disallow using async/await in Cypress before methods
no-async-tests	disallow using async/await in Cypress test cases	✅
no-force	disallow using force: true with action commands
no-pause	disallow using cy.pause() calls
no-unnecessary-waiting	disallow waiting for arbitrary time periods	✅
require-data-selectors	require data-* attribute selectors
unsafe-to-chain-command	disallow actions within chains	✅

Mocha and Chai

Cypress is built on top of Mocha and Chai. See the following sections for information on using ESLint plugins eslint-plugin-mocha and eslint-plugin-chai-friendly together with eslint-plugin-cypress.

Mocha .only and .skip

During test spec development, Mocha exclusive tests .only or Mocha inclusive tests .skip may be used to control which tests are executed, as described in the Cypress documentation Excluding and Including Tests. To apply corresponding rules, you can install and use eslint-plugin-mocha. The rule mocha/no-exclusive-tests detects the use of .only and the mocha/no-skipped-tests rule detects the use of .skip:

npm install --save-dev eslint-plugin-mocha

In your .eslintrc.json:

{
  "plugins": [
    "cypress",
    "mocha"
  ],
  "rules": {
    "mocha/no-exclusive-tests": "warn",
    "mocha/no-skipped-tests": "warn"
  }
}

Or you can simply use the cypress/recommended and mocha/recommended configurations together, for example:

{
  "extends": [
    "plugin:cypress/recommended",
    "plugin:mocha/recommended"
  ]
}

Chai and no-unused-expressions

Using an assertion such as expect(value).to.be.true can fail the ESLint rule no-unused-expressions even though it's not an error in this case. To fix this, you can install and use eslint-plugin-chai-friendly.

npm install --save-dev eslint-plugin-chai-friendly

In your .eslintrc.json:

{
  "plugins": [
    "cypress",
    "chai-friendly"
  ],
  "rules": {
    "no-unused-expressions": 0,
    "chai-friendly/no-unused-expressions": 2
  }
}

Or you can simply add its recommended config:

{
  "extends": ["plugin:chai-friendly/recommended"]
}

Contributing

Please see our Contributing Guideline which explains how to contribute rules or other fixes and features to the repo.