test(react-virtual): wait for smooth scrolls to settle instead of a fixed 2s - #1289
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piecyk merged 2 commits intoSep 14, 2026
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…ixed 2s "smooth scrolls to index 1000" flaked on CI (TanStack#1280 at 83bdf23, which had passed two days earlier on the same commit, and TanStack#1248 before it). A smooth scroll's duration scales with distance — index 1000 is ~50,000px — and reconcileScroll may re-drive it as rows measure; under 6x CPU throttling the scroll arrives ~2.2s after the click, past the fixed 2s wait, and the target row is not rendered yet. Replace every fixed wait with a helper that waits for the target row to be visible and for scrollTop to stop moving, with a generous timeout. The 200ms mid-animation interrupt in the last test is kept: it is part of the scenario, not a settle wait. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
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Included review availability: Your plan provides up to 8 included reviews per hour; 7 remain after this review. 📝 WalkthroughWalkthroughThe smooth-scroll E2E app exposes its virtualizer on ChangesSmooth-scroll test synchronization
Priority: ⬇️ Low Estimated code review effort: 2 (Simple) | ~10 minutes Change: Other Merge Risk: ⚪ Minimal · up to This change only improves smooth-scroll E2E synchronization and does not affect release behavior. 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
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In `@packages/react-virtual/e2e/app/test/smooth-scroll.spec.ts`:
- Around line 2-33: Update waitForSmoothScroll to use a reliable
scroll-completion or target-settlement signal rather than returning after two
equal scrollTop samples. Account for reconcileScroll re-driving smooth scrolling
as rows measure, while preserving the existing target-row visibility wait and
timeout behavior.
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… equal samples Review follow-up. Two scrollTop samples 100ms apart can straddle the pause between two reconcileScroll re-drives, so equal samples do not prove the smooth scroll has completed. The virtualizer has the real signal: reconcileScroll retires `scrollState` only once the target is stable and reached. Expose the instance on the fixture page and wait for `scrollState === null && !isScrolling` after the target row is visible, keeping the 15s ceiling. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
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smooth scrolls to index 1000flaked on CI: #1280 at 83bdf23 failed on it two days after the identical commit passed, and #1248's run failed on it too. A smooth scroll's duration scales with distance (index 1000 is ~50,000px) andreconcileScrollmay re-drive it as rows measure. Under 6x CPU throttling locally the scroll arrives ~2.2s after the click, just past the fixed 2s wait, with the target row not rendered yet.🎯 Changes
smooth-scroll.spec.ts: replace every fixedwaitForTimeout(2000)+toBeVisible()pair withwaitForSmoothScroll(page, testId), which waits for the target row to be visible and forscrollTopto stop moving, with a 15s ceiling. The 200ms mid-animation interrupt in the last test is kept since it is part of the scenario.Test-only; 14/14 passing locally on two repeats.
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