test(query-core): assert exact values instead of loose matchers in remaining tests

[reizam]

🎯 Changes

Continues the recent test-quality series (e.g. #11057, #11043, #11048) by converting the remaining toBeTruthy() / toBeFalsy() / toBeDefined() assertions in query-core tests to exact assertions:

• queryCache.find(...) presence checks now assert the exact cached value (?.state.data) or status (?.state.status) produced at that point of the test, and absence checks use toBeUndefined() instead of toBeFalsy()/not.toBeDefined().
• isPaused boolean check uses toBe(true).
• error?.message.includes(...) + toBeTruthy() becomes toContain(...) for a precise failure message.
• Cache event queries in queryCache.test.tsx now assert reference identity against the cached query (toBe(cachedQuery)) instead of mere existence.
• Three redundant existence checks (expect(state).toBeTruthy() / expect(args).toBeDefined()) were removed where the neighboring exact assertions already fail on an undefined object.

After this, grep -rE 'toBeTruthy\(\)|toBeFalsy\(\)|toBeDefined\(\)' packages/query-core/src returns no matches.

✅ Checklist

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

Local verification detail: vitest run in packages/query-core — 24 files, 554 tests passed, no type errors; test:eslint and prettier clean; test:types green on all six TypeScript versions (5.4 → 5.9).

🚀 Release Impact

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

[coderabbitai]

📝 Walkthrough

Walkthrough

Changes

Query-core assertion tightening

Layer / File(s)	Summary
Hydration and cache result assertions packages/query-core/src/__tests__/hydration.test.tsx, packages/query-core/src/__tests__/queriesObserver.test.tsx, packages/query-core/src/__tests__/queryCache.test.tsx	Hydration tests assert exact data and exclusion of unsuccessful queries; cache tests verify query identity and prefetched data.
Query lifecycle state assertions packages/query-core/src/__tests__/query.test.tsx	Garbage-collection tests assert specific query states and retained data, while the serialization error matcher uses toContain.
Query client lifecycle assertions packages/query-core/src/__tests__/queryClient.test.tsx	Prefetch, removal, reset, and paused-mutation tests assert explicit data, state, and cache outcomes.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• TanStack/query#11043: Tightens query-core paused-mutation and hydration assertions.
• TanStack/query#11049: Replaces loose truthiness checks with explicit query state assertions.
• TanStack/query#11053: Tightens QueryCache event and payload assertions.

Suggested reviewers: sukvvon, tkdodo

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
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.
Title check	✅ Passed	The title clearly matches the PR’s main change: tightening query-core tests to exact assertions instead of loose matchers.
Description check	✅ Passed	The description follows the required template and includes changes, checklist, and release impact with relevant details.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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