e2e-testing

From the author

Build and keep end-to-end suites that are worth their runtime — which journeys belong at this level, selectors that survive refactors, waiting on state instead of sleeping, per-spec data isolation, and flake triage that finds the cause. Use when adding or repairing an e2e suite, when specs are slow or intermittently red, or when deciding whether a case belongs here at all. Not for one-off checking that a change renders, not for unit or integration tests, and not for load testing.