Fixing flaky Playwright tests: root causes and reliable solutions

Short summary

Flaky Playwright tests are deterministic bugs with hidden triggers, not random noise. The main causes include improper wait conditions, animation timing, shared state between tests, external API dependencies, and CI resource starvation. Fixes include asserting on meaningful DOM signals, clearing state in beforeEach, mocking third-party calls, and replacing fixed timeouts with condition-based waits.

• •Flaky tests are non-deterministic bugs from unaccounted state, timing, or order dependencies
• •Wait on real signals (visibility, opacity, aria-busy) instead of assuming instant readiness
• •Clear cookies and state in beforeEach; mock external APIs; avoid waitForTimeout in CI

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