Quick reference
The highest-impact habits from this guide, grouped by where they apply: writing tests, building them to last, and running them efficiently.
Write
Test what users see, not implementation details
Keep every test isolated, with its own data and context
Build
Prefer user-facing locators over CSS or XPath
Use web-first assertions that retry automatically
Generate locators with codegen when you're unsure
Run & debug
Test across all three browser engines
Debug CI failures with the trace viewer
Run tests in parallel, sharded across machines