Fixture Architecture Playbook

• Build helpers as pure functions first, then expose them via Playwright extend or Cypress commands so logic stays testable in isolation.
• Compose capabilities with mergeTests (Playwright) or layered Cypress commands instead of inheritance; each fixture should solve one concern (auth, api, logs, network).
• Keep HTTP helpers framework agnostic—accept all required params explicitly and return results so unit tests and runtime fixtures can share them.
• Export fixtures through package subpaths ("./api-request", "./api-request/fixtures") to make reuse trivial across suites and projects.
• Treat fixture files as infrastructure: document dependencies, enforce deterministic timeouts, and ban hidden retries that mask flakiness.

Source: Murat Testing Philosophy, cy-vs-pw comparison, SEON production patterns.