End-to-end testing

End-to-end (E2E) testing validates the entire application flow: simulating a real user's critical journey from the UI down to the database and all external dependencies.

E2E testing confirms your system functions correctly across the full technology stack. This is the top layer of the testing pyramid, focusing on complete user workflows (e.g., login, search, checkout) rather than isolated units. The process replicates real-world scenarios: a test might start at the user interface, pass through the application logic, interact with a database, and verify communication with an external API like a payment gateway. This method is critical for complex, multi-layered applications, ensuring data integrity and subsystem interactions perform reliably before deployment.

https://www.testim.io/blog/end-to-end-testing-the-one-guide-to-rule-them-all/