Glossary

E2E Testing

E2E (End-to-End) tests automatically simulate real user actions in a browser: fill in a form, click a button, verify that data appears. They test the entire stack from UI to database.

When needed

Critical flows: registration, login, checkout, payment
Complex multi-step UI flows
Regression tests after major changes

Popular tools

Playwright (Microsoft) — supports Chromium, Firefox, WebKit. The most popular today
Cypress — JavaScript, excellent DX, Chromium-based only
Selenium — older, supports all browsers

Downsides

E2E tests are slow (seconds per test), brittle (depend on UI details), and require a running application. Keep them few and run them less frequently than unit tests.