test: Migrate to Vitest

[timfish]

This PR:

• Migrates all tests to Vitest
• I had to change the CI cache keys because changing a package.json resulted in no lock change and a build failure
• Test usages of the Vite plugin had to add as unknown as vite.Plugin because the Vite versions varied between the plugin and integration tests. This does not impact end users because it will use their Vite version.

[github-actions]

Semver Impact of This PR

⚪ None (no version bump detected)

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• test: Migrate to Vitest by timfish in #882

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Cursor Bugbot has reviewed your changes and found 1 potential issue.

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CI runs integration tests on unsupported Node 18

High Severity

The test-integration CI matrix includes Node 18 ([18, 20, 22, 24]), but packages/integration-tests/package.json now depends on "vitest": "^4.0.0", which requires Node ^20.0.0 || ^22.0.0 || >=24.0.0. Integration tests running on Node 18 in CI will fail. The PR description explicitly says integration tests are excluded from the Vitest migration to retain Node 18 support, but the migration was applied to them as well.

Additional Locations (1)

• packages/integration-tests/package.json#L34-L35

 

[timfish]

The tests seem to be passing fine!

[chargome]

Looks good! Just double checking: in the descr you mentioned migrating to vitest apart from the integration tests but this pr does migrate them right?

[timfish]

Ah yes, I'll update that!

Just realised this PR doesn't update the e2e snapshots and these didn't run and fail in CI because it's from a fork.