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

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

Usage

Add an .eslintrc.json file to your cypress directory with the following:

{
  "plugins": [
    "cypress"
  ]
}

You can add rules:

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

You can whitelist 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"
  ]
}

Rules

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

Rules with a check mark (✅) are enabled by default while using the plugin:cypress/recommended config.

NOTE: These rules currently require eslint 5.0 or greater. If you would like support added for eslint 4.x, please 👍 this issue.

	Rule ID	Description
✅	no-assigning-return-values	Prevent assigning return values of cy calls
✅	no-unnecessary-waiting	Prevent waiting for arbitrary time periods
	assertion-before-screenshot	Ensure screenshots are preceded by an assertion

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
  }
}

Contribution Guide

To add a new rule:

• Fork and clone this repository
• Generate a new rule (a yeoman generator is available)
• Run yarn start or npm start
• Write test scenarios then implement logic
• Describe the rule in the generated docs file
• Make sure all tests are passing
• Add the rule to this README
• Create a PR

Use the following commit message conventions: https://github.com/semantic-release/semantic-release#commit-message-format