test: add hydration tests

[danielroe]

wanting to fix some hydration issues and add regression tests to avoid them recurring

• fix(core): always return ssrValue in useCssSupports before mounted vueuse/vueuse#5290
• fix(ui): invalid html button markup #1274

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Project	Deployment	Actions	Updated (UTC)
docs.npmx.dev	Error		Feb 9, 2026 4:58pm
npmx.dev	Ready	Preview, Comment	Feb 9, 2026 4:58pm

1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
npmx-lunaria	Ignored		Feb 9, 2026 4:58pm

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

📢 Thoughts on this report? Let us know!

[coderabbitai]

📝 Walkthrough

Walkthrough

This pull request introduces hydration debugging capabilities and comprehensive testing infrastructure. The changes include adding a new $test configuration property to the Nuxt config that enables hydration debugging, creating a new end-to-end test suite that validates hydration behaviour across multiple localStorage configurations, extending the test fixture type to capture hydration error messages from the console, and updating a component reference in the accessibility test skip list from ScrollToTop.vue to ScrollToTop.client.vue.

Possibly related PRs

• test: mock client side requests in lighthouse #1171: Modifies the test fixture signature in test/e2e/test-utils.ts with the mockExternalApis fixture, providing the foundation for hydrationErrors fixture extension.

Suggested labels

front

Suggested reviewers

• firstangler59

🚥 Pre-merge checks | ✅ 1

✅ Passed checks (1 passed)

Check name	Status	Explanation
Description check	✅ Passed	The pull request description clearly indicates the intent to fix hydration issues and add regression tests, which directly aligns with the changeset containing hydration configuration, test utilities, and comprehensive e2e test suite.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/hydration

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No actionable comments were generated in the recent review. 🎉

🧹 Recent nitpick comments

test/e2e/hydration.spec.ts (1)

118-124: Consider exporting injectLocalStorage from test-utils.ts for reuse.

This helper is well-implemented and could benefit other E2E tests that need to seed localStorage before navigation. Using addInitScript is the correct approach as it executes before any page scripts run.

♻️ Suggested refactor to move helper to test-utils

In test/e2e/test-utils.ts:

export async function injectLocalStorage(page: Page, entries: Record<string, string>) {
  await page.addInitScript((e: Record<string, string>) => {
    for (const [key, value] of Object.entries(e)) {
      localStorage.setItem(key, value)
    }
  }, entries)
}

Then import in hydration.spec.ts:

-import type { Page } from '@playwright/test'
-import { expect, test } from './test-utils'
+import { expect, test, injectLocalStorage } from './test-utils'

And remove the local definition.

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