test(virtual-core): split index.test.ts into topic files by piecyk · Pull Request #1328 · TanStack/virtual

piecyk · 2026-10-15T06:42:52Z

🎯 Changes

packages/virtual-core/tests/index.test.ts had grown to ~7000 lines with ~230 flat tests. This PR moves the tests into one file per topic. Test bodies and names are unchanged.

 packages/virtual-core/tests/
-├── index.test.ts            # 6985 lines, everything
+├── index.test.ts            # exports, lanes, setOptions, takeSnapshot
+├── scroll-commands.test.ts  # scrollToIndex/Offset/By, reconcile, cancelScroll, read-backs
+├── measurement.test.ts      # resizeItem, measure(), ResizeObserver cache + batching
+├── range.test.ts            # defaultRangeExtractor, lazy fast path
+├── ios-deferral.test.ts     # iOS deferred corrections, touch phases, Phase 2a/2b, #1250
+├── ios-fling-wait.test.ts   # iOS 27 commands that wait for a fling tail
+├── adjustment.test.ts       # scroll-up jank, self-write direction latch, #1218
+├── anchor-end.test.ts       # anchorTo end, followOnAppend, #1229, #1258
+├── dom-observers.test.ts    # elementScroll/windowScroll, observeElement/WindowOffset
+├── helpers.ts               # helpers used by more than one file
 ├── ios-gesture.test.ts      # (unchanged)
 ├── prepend-hold.test.ts     # (unchanged)
 └── ...

Each top-level block (test, helper, section comment) moved whole, by line range.
Only 3 helpers are used by more than one file and move to helpers.ts with export: withFakeIOSUserAgent, makeDeferralHarness, makeMockScrollElement. All other helpers stay next to their tests.

Evidence

Before: vitest on main → 408 tests, 407 passed, 1 skipped.
After: vitest on this branch → 408 tests, 407 passed, 1 skipped. The set of (fullName, status) pairs is identical.
Every non-blank line of the old file appears exactly once in the new files. The only edit is the export keyword on the 3 shared helpers.
A type check that includes tests/ gives the same error count before and after (the existing errors come from loose test mocks; tests/ is not part of test:types).

Merge Danger

Door: two-way

Tests only. A revert restores the single file.

Blast Radius: open-PRs

No published code changes. Open PRs that edit index.test.ts will conflict and need a rebase that moves their new tests into the matching topic file:

✅ Checklist

I have followed the steps in the Contributing guide.
I have tested this code locally with pnpm run test:pr.

🚀 Release Impact

This change affects published code, and I have generated a changeset.
This change is docs/CI/dev-only (no release).

🤖 Generated with Claude Code

Summary by CodeRabbit

Tests
- Expanded coverage for virtualized list scrolling, including scroll adjustments, anchoring, end-follow behavior, and scroll commands.
- Added tests for iOS touch and fling behavior, measurement updates, range extraction, DOM observers, and cleanup.

index.test.ts had grown to ~7000 lines with ~230 flat tests. Move the tests into one file per topic, without changing any test: - scroll-commands: scrollToIndex/Offset/By, reconcile, cancelScroll, read-backs - measurement: resizeItem, measure(), ResizeObserver cache and batching - range: defaultRangeExtractor and the lazy fast path - ios-deferral: iOS deferred corrections, touch phases, Phase 2a/2b, TanStack#1250 - ios-fling-wait: iOS 27 commands that wait for a fling tail - adjustment: scroll-up jank, self-write direction latch, TanStack#1218 - anchor-end: anchorTo end, followOnAppend, TanStack#1229, TanStack#1258 - dom-observers: elementScroll/windowScroll, observeElement/WindowOffset - index: exports, lanes, setOptions, takeSnapshot Helpers used by more than one file move to tests/helpers.ts; the others stay next to their tests. Test bodies and names are unchanged; vitest reports the same 408 tests before and after. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

changeset-bot · 2026-10-15T06:42:59Z

⚠️ No Changeset found

Latest commit: 7b77c3e

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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coderabbitai · 2026-10-15T06:43:32Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Configuration used: defaults
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Plan: Advanced
Run ID: 0a9c4e94-e7b9-4215-9290-5b346c5c022d

📥 Commits

Reviewing files that changed from the base of the PR and between 77cb05e and 7b77c3e.

📒 Files selected for processing: 10

packages/virtual-core/tests/adjustment.test.ts
packages/virtual-core/tests/anchor-end.test.ts
packages/virtual-core/tests/dom-observers.test.ts
packages/virtual-core/tests/helpers.ts
packages/virtual-core/tests/index.test.ts
packages/virtual-core/tests/ios-deferral.test.ts
packages/virtual-core/tests/ios-fling-wait.test.ts
packages/virtual-core/tests/measurement.test.ts
packages/virtual-core/tests/range.test.ts
packages/virtual-core/tests/scroll-commands.test.ts

Included review availability: This review used your included allowance. Your plan provides up to 8 included reviews per hour; 6 remain after this review.

📝 Walkthrough

This pull request adds virtual-core tests for measurement, scroll adjustment and commands, end anchoring, DOM observers, and iOS touch and fling handling.

Changes: Virtualizer behavior coverage

Layer / File(s)	Summary
Measurement and range access `packages/virtual-core/tests/measurement.test.ts`, `packages/virtual-core/tests/range.test.ts`	Tests cover measurement cache updates, ResizeObserver behavior, lazy measurements, and range extraction.
DOM scroll observers `packages/virtual-core/tests/dom-observers.test.ts`	Tests cover scroll calls and offsets, listener cleanup, and virtualizer scroll-state resets.
Scroll adjustment behavior `packages/virtual-core/tests/adjustment.test.ts`	Tests cover adjustment direction, read-backs, notification timing, and measurements of viewport-spanning items.
Scroll command reconciliation `packages/virtual-core/tests/scroll-commands.test.ts`	Tests cover command targets, reconciliation and cancellation, end alignment, measurement changes, and scroll-element replacement.
End anchoring and append behavior `packages/virtual-core/tests/anchor-end.test.ts`	Tests cover reading-anchor preservation, append following, end-distance calculations, and retries for clamped anchor writes.
iOS scroll deferral and fling handling `packages/virtual-core/tests/helpers.ts`, `packages/virtual-core/tests/ios-deferral.test.ts`, `packages/virtual-core/tests/ios-fling-wait.test.ts`	Helpers and tests cover deferred corrections, touch and momentum states, queued index commands, fling outcomes, and cleanup.

Priority: ⬇️ Low

Estimated code review effort: 4 (Complex) | ~60 minutes

Change: Other

Merge Risk: ⚪ Minimal · up to 7b77c

This change only reorganizes the virtual-core test suite into topic-based files, with no change to library code or published behavior. It carries no meaningful merge risk.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 72.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 25 functions across 9 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Title check		The title clearly and concisely describes the main change: splitting the monolithic virtual-core test file into topic-specific files.
Description check		The description explains the scope, motivation, file organization, validation results, merge impact, checklist, and release impact. The checklist boxes remain unchecked, but the required information i…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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packages/virtual-core/tests/adjustment.test.ts

Parsing error: "parserOptions.project" has been provided for @typescript-eslint/parser.
The file was not found in any of the provided project(s): packages/virtual-core/tests/adjustment.test.ts

packages/virtual-core/tests/anchor-end.test.ts

Parsing error: "parserOptions.project" has been provided for @typescript-eslint/parser.
The file was not found in any of the provided project(s): packages/virtual-core/tests/anchor-end.test.ts

packages/virtual-core/tests/dom-observers.test.ts

Parsing error: "parserOptions.project" has been provided for @typescript-eslint/parser.
The file was not found in any of the provided project(s): packages/virtual-core/tests/dom-observers.test.ts

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nx-cloud · 2026-10-15T06:43:53Z

View your CI Pipeline Execution ↗ for commit 7b77c3e

Command	Status	Duration	Result
`nx affected --targets=test:sherif,test:knip,tes...`	✅ Succeeded	4m 15s	View ↗
`nx run-many --target=build --exclude=examples/**`	✅ Succeeded	20s	View ↗

☁️ Nx Cloud last updated this comment at 2026-10-15 06:47:57 UTC

pkg-pr-new · 2026-10-15T06:44:15Z

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commit: 7b77c3e

piecyk merged commit 16c786a into TanStack:main Oct 15, 2026
10 checks passed

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test(virtual-core): split index.test.ts into topic files - #1328

test(virtual-core): split index.test.ts into topic files#1328
piecyk merged 1 commit into
TanStack:mainfrom
piecyk:test/split-core-tests

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