End-to-End Testing — Engineering Skill

Standards for a browser end-to-end suite: how tests find elements, where their data comes from, what they mock, how they wait, and how the suite stays fast and trustworthy. Framework-neutral — the rules hold for Playwright and Cypress; examples use Playwright syntax with the Cypress equivalent noted where it differs.

Builds on. test-quality for whether an individual test is worth keeping (one outcome per test, a meaningful assertion, determinism) and architecture-and-design for suite strategy — how thin the e2e layer should be relative to integration and unit. On a conflict, test-quality decides the individual test and this skill decides the e2e mechanics. Load a sibling only when the task turns on its layer; if it is not loaded, apply that layer from general knowledge and do not block.

This SKILL.md is self-sufficient: the Ruleset below is the complete, enforceable list. Each references/<topic>.md holds that group's reasoning and ❌ / ✅ code, and references/worked-example.md a full review pass; open them for depth when your runtime allows.