test({react,preact}-query/usePrefetchQuery): use the '.then()' convention consistently

[Antoliny0919]

🎯 Changes

Two queryFn.mockImplementationOnce overrides in usePrefetchQuery.test.tsx are still written with async/await, while the base implementation of the very same queryFn already uses.then().
#10399 / #10400 converted the mockImplementation of the shared generateQueryFn helper in these files, so these look like leftovers from that pass , they appear to be the last mockImplementationOnce(async ...) in the repo.

The rejection happens strictly after sleep(10) resolves, so the timing is unchanged.
Would it make sense to switch them to match the convention 🤔

✅ 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).

Summary by CodeRabbit

• Tests
  • Updated prefetch error-handling tests to more reliably simulate delayed server failures.
  • Preserved coverage for failed-query behavior, retry handling, and recovery flows.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 7cdf0607-052d-416b-a8e6-ae46b6ab9e5a

📥 Commits

Reviewing files that changed from the base of the PR and between 181ea82 and d8bd850.

📒 Files selected for processing (2)

• packages/preact-query/src/__tests__/usePrefetchQuery.test.tsx
• packages/react-query/src/__tests__/usePrefetchQuery.test.tsx

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📝 Walkthrough

Walkthrough

Updated React and Preact usePrefetchQuery error tests to produce delayed query failures through promise chains instead of async/await mocks. Test expectations, component wiring, and recovery behavior remain unchanged.

Changes

Prefetch error test updates

Layer / File(s)	Summary
Promise-chain error mocks packages/{react-query,preact-query}/src/__tests__/usePrefetchQuery.test.tsx	The two failing queryFn mocks in each package now return sleep(10).then(...) and throw the same server error inside the callback.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Possibly related PRs

• TanStack/query#11080: Refactors delayed queryFn implementations in the same prefetch tests.
• TanStack/query#11085: Standardizes test mocks around .then() promise chains.
• TanStack/query#11088: Replaces async/await delays with returned sleep(...).then(...) callbacks.

Suggested reviewers: sukvvon

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the test-only switch from async/await to .then() in usePrefetchQuery tests.
Description check	✅ Passed	The description matches the template with Changes, Checklist, and Release Impact, and the key details are filled in.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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