testinglisted

# Testing Use this skill when work requires automated verification, regression protection, test design, or test maintenance. This skill is language and framework agnostic. ## Principles Test observable behavior rather than internal implementation details whenever practical. Prefer the smallest test scope that gives useful confidence. Use: - unit tests for isolated logic - integration tests for boundaries between components - contract tests for external interfaces - end-to-end tests only where broader system behavior must be proven Do not require every behavior to be tested at every layer. #### Browser E2E Playwright Regression Use browser or end-to-end regression tests when important behavior can only be proven through the rendered application, real navigation, browser state, client-side interactions, or frontend/backend wiring. Browser regression coverage may be appropriate for: - critical user journeys - form validation and submission behavior - authentication-dependent navigation - frontend/backend contract wiring - client-side state transitions - browser-only rendering failures - responsive behavior that has broken before - accessibility-critical interaction paths Use the project's existing browser test tool when available. Playwright is a good default when the project already uses it or when the user asks for it, but do not introduce it solely because a browser was useful for manual inspection. Prefer resilient user-facing locators, deterministic setup, web