cypress-io/cypress

Cypress is a testing framework for web applications that runs in the browser. Its core purpose is to let developers write automated tests that simulate how a real user would interact with their website, clicking buttons, filling in forms, navigating between pages, and verifying that the right things appear on screen, all without any manual effort each time the code changes. Unlike older testing tools that ran outside the browser and communicated with it indirectly, Cypress runs its test code directly inside the browser alongside the application. This gives it reliable access to the application's internal state, makes it easier to inspect what is happening when a test fails, and eliminates many sources of flakiness that plagued older approaches. Tests are written in JavaScript or TypeScript, and the Cypress API uses a readable chaining style where you describe what to do and what to check in a sequence of commands. Cypress supports two types of testing: end-to-end tests that load the whole app in a real browser and simulate user journeys, and component tests that mount individual UI components in isolation to test them without loading the entire application. You would use Cypress when you want to automatically verify that your web application works correctly from a user's perspective after every code change, catching regressions before they reach users. It is particularly popular with teams building React, Angular, Vue, or Svelte applications. The tool is installed as a Node.js package via npm, yarn, or pnpm, and it opens a visual test runner for local development where you can watch tests execute step by step. The tech stack is TypeScript and Node.js, running tests inside real Chromium-based browsers or Firefox.