End-to-end tests

An end-to-end test opens the site, signs up with a test account, adds a product to the cart and checks that the order confirmation appears. Because it exercises the frontend, backend, database and outside services together, a passing run is strong evidence that the whole journey works. Playwright and Cypress are the usual tools; Puppeteer suits lighter automation.

They are the slowest and most fragile layer: timing, test data and third-party services can make a test fail now and then for no real reason (a flaky test). Teams keep them to the critical journeys, such as sign-in, checkout and payments, run them against a preview or staging deployment in CI, and use traces, screenshots and videos to debug failures.