Playwright's auto-retry hid a UI flash bug — MutationObserver test caught it
SeanOliver · x · 2026-10-23
Sean Oliver shares a testing lesson: Playwright's toContainText retries until it passes, so e2e tests never see the flash of stale values. He uses a MutationObserver test recording the row when edit mode ends — it fails on old code ("London") and passes with the fix. The fix keeps saved values on screen until the rows prop changes, with the overlay remembering which rows array it saved against, so it switches off on first refresh without cleanup code.
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