playwright-core

# Playwright Core Testing > Opinionated, production-tested Playwright guidance — every pattern includes when (and when *not*) to use it. **46 reference guides** covering the full Playwright testing surface: selectors, assertions, fixtures, network mocking, auth, visual regression, accessibility, API testing, debugging, and more — with TypeScript and JavaScript examples throughout. ## Golden Rules 1. **`getByRole()` over CSS/XPath** — resilient to markup changes, mirrors how users see the page 2. **Never `page.waitForTimeout()`** — use `expect(locator).toBeVisible()` or `page.waitForURL()` 3. **Web-first assertions** — `expect(locator)` auto-retries; `expect(await locator.textContent())` does not 4. **Isolate every test** — no shared state, no execution-order dependencies 5. **`baseURL` in config** — zero hardcoded URLs in tests 6. **Retries: `2` in CI, `0` locally** — surface flakiness where it matters 7. **Traces: `'on-first-retry'`** — rich debugging artifacts without CI slowdown 8. **Fixtures over globals** — share state via `test.extend()`, not module-level variables 9. **One behavior per test** — multiple related `expect()` calls are fine 10. **Mock external services only** — never mock your own app; mock third-party APIs, payment gateways, email ## Guide Index ### Writing Tests | What you're doing | Guide | Deep dive | |---|---|---| | Choosing selectors | [locators.md](locators.md) | [locator-strategy.md](locator-strategy.md) | | Assertions & waiting | [assertion...