Migrate to Vitest 5

[Copilot]

Migrates the test infrastructure from Vitest 4 to Vitest 5 while preserving existing test behavior.

Changelog

New

• None

Changed

• Upgrade vitest, @vitest/browser, and @vitest/browser-playwright to v5.
• Align the shared Vitest configuration peer dependency.
• Temporarily exempt newly released Vitest packages and tinybench from npm’s release-age policy.
• Replace a timer-based SelectPanel assertion with waitFor to account for asynchronous updates.

Removed

• None

Rollout strategy

• Patch release
• Minor release
• Major release; if selected, include a written rollout or migration plan
• None; development dependency and test-only changes

Testing & Reviewing

Review the dependency graph, temporary release-age exclusions, and Vitest 5 migration compatibility.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 80ae74a

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.

This PR includes no changesets

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[github-actions]

⚠️ Action required

👋 Hi, this pull request contains changes to the source code that github/github-ui depends on. If you are GitHub staff, test these changes with github/github-ui using the integration workflow. Check the integration testing docs for step-by-step instructions. Or, apply the integration-tests: skipped manually label to skip these checks.

[joshblack]

Suggested change

	min-release-age-exclude[]=vitest
	min-release-age-exclude[]=@vitest/*
	min-release-age-exclude[]=tinybench

[Copilot]

🟡 Changes recommended

Vitest 5’s Node engine floor (>=22.12) appears to conflict with the repo’s declared Node engine support (allows 22.11), which should be aligned to prevent install/test issues.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Migrates the repo’s test tooling from Vitest 4 to Vitest 5, keeping existing behavior stable while accounting for Vitest’s new package set and some async timing differences in tests.

Changes:

• Upgrades vitest, @vitest/browser, and @vitest/browser-playwright to ^5.0.0 and aligns the internal @primer/vitest-config peer dependency.
• Adds npm min-release-age exclusions for the newly released Vitest packages and tinybench to avoid install blocks during the initial release window.
• Updates a SelectPanel test to use waitFor instead of a 0ms timer tick to accommodate async updates.

File summaries

File	Description
packages/vitest-config/package.json	Bumps the internal shared config’s vitest peer dependency to v5.
packages/react/src/SelectPanel/SelectPanel.test.tsx	Replaces a timer-based assertion with waitFor for async stability.
package.json	Updates root devDependencies to Vitest 5-related packages.
package-lock.json	Lockfile updates reflecting Vitest 5 and its updated dependency tree (including new engine constraints).
.npmrc	Temporarily exempts Vitest-related packages and tinybench from npm’s release-age policy.

Review details

• Files reviewed: 4/5 changed files
• Comments generated: 0
• Review effort level: Lite

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[primer-integration]

Integration test results from github/github-ui PR:

  CI Passed
  VRT Passed
  Projects Passed

All checks passed!