How does Cypress work?

It is a web and API end-to-end (E2E) testing automation tool that runs directly in the browser, which sets it apart from other testing tools. The way it works is key to its efficiency and popularity.

Runs within the same browser environment

When you run a test, it integrates directly into the browser where your application is loaded.

This means it has full access to:
DOM (HTML structure)
Network (HTTP/HTTPS requests)
Local storage and cookies
Browser events

💡 Think of Cypress as a co-pilot sitting inside the car (browser) with access to everything that's going on. It can see the dashboard (DOM), hear the commands (events), and even adjust the controls (like modifying cookies).

Executes tests in real-time

It doesn't use WebDriver (unlike tools like Selenium). It runs directly in the same event loop as the browser.
This allows tests to be fast, reliable, and synchronized
because:
There's no delay in communication between the test and the browser.
It knows exactly when elements are available or when requests have finished, without needing "manual waits."

💡 If you ask Selenium to check if a button is visible, it has to ask the browser and wait for a response. Cypress "looks with its own eyes" inside the browser and knows immediately.

Instant feedback

When a test fails, Cypress shows exactly:
What went wrong (e.g., element not found)
The state of the application at the time of the error (e.g., DOM, console, network)
You can even replay the steps manually in the visual interface to understand the problem.

Powerful and easy-to-use features

It makes writing tests much easier with:
Chained commands (cy.get().click())
Automatic waits (no need for sleep, it waits for elements to appear or requests to finish)
Event simulation like clicks, typing, and scrolling
API interception (mocking or validating requests)

Why is it so good?

Easy to set up

Just install with a single command (npm install cypress) and start writing tests, no complex configurations needed.
It runs directly in the browser, so there's no need to install additional drivers.

Fast and reliable

Since it runs in the same environment as the application, it avoids synchronization issues. Sometimes with Selenium, the test might fail not because it's poorly written or the application crashed, but because Selenium couldn't connect — this doesn't happen with Cypress.

Integrated features