What is e2e?
e2e stands for “end‑to‑end.” In tech it usually describes a process that covers everything from the very start to the very finish without any gaps. The most common use is “end‑to‑end testing,” where a test checks a whole user flow (like signing up, buying a product, and receiving a receipt) as a single, complete scenario.
Let's break it down
- End: The first point of interaction (e.g., a user opening a web page).
- To: The connection between the start and the finish.
- End: The final outcome (e.g., the user sees a confirmation). In e2e testing you simulate a real user’s actions, let the system run through all its layers (UI, API, database, external services), and verify the final result is correct.
Why does it matter?
Because it shows whether the whole system works together, not just isolated parts. A unit test might confirm a single function works, but an e2e test tells you if a user can actually complete a task without errors. This helps catch integration bugs early and builds confidence that the product is ready for real users.
Where is it used?
- Web and mobile applications (e.g., testing a checkout flow).
- SaaS platforms that combine many micro‑services.
- APIs that need to be verified from request to response.
- Continuous integration pipelines, where e2e tests run automatically on every code change.
Good things about it
- Real‑world confidence: Mimics actual user behavior.
- Early bug detection: Finds problems that unit or integration tests miss.
- Documentation: Serves as living documentation of key user journeys.
- Automation friendly: Can be run automatically in CI/CD pipelines.
Not-so-good things
- Slow: Running through the whole UI and backend takes more time than small tests.
- Flaky: Tests can fail due to timing issues, network hiccups, or UI changes, leading to false alarms.
- Complex to maintain: When the UI or workflow changes, many e2e tests may need updates.
- Resource heavy: Requires browsers, test servers, and sometimes mock services, increasing infrastructure cost.