test(api-compare): verify dark and light prefers-color-scheme visual cohesion #4431

[Rakshak05]

Closes #4431

Description

This PR introduces isolated unit and integration testing targeting Dark and Light Prefers-Color-Scheme Visual Cohesion for the comparison API route (app/api/compare/route.ts).

Specifically, it creates the new test file app/api/compare/route.theme-contrast.test.ts implementing the following 5 test cases:

1. Dual-theme environment mock: Mocks window.matchMedia for both dark and light settings to verify that the JSON response payload carries no hardcoded color tokens (hex values, rgb/rgba, or Tailwind color classes).
2. Color contrast validation: Asserts that all simulated API error responses (404, 403, 500, 502) contain only plain text and do not smuggle presentation-level styles (such as ANSI escape codes, style/class attributes, or zero-width characters) that would break client-side contrast enforcement.
3. Tailwind/stylesheet class checks: Checks that the response headers carry no custom presentational headers (e.g., X-Theme or X-Color-Scheme) and that Content-Type is strictly application/json, leaving theme styling controls fully to the client.
4. Background overlay check: Verifies that successful API payloads return fully populated user objects to prevent consuming UI cards from rendering as empty, background-colored overlay containers.
5. Visual cohesion headers check: Passes dark and light Sec-CH-Prefers-Color-Scheme client headers to verify that the API returns structurally identical payloads in both modes.

Pillar

• 🎨 Pillar 1 — New Theme Design
• 📐 Pillar 2 — Geometric SVG Improvement
• 🕐 Pillar 3 — Timezone Logic Optimization
• 🛠️ Other (Bug fix, refactoring, docs, testing)

Visual Preview

N/A (Backend / API Tests)

Checklist before requesting a review:

• I have read the CONTRIBUTING.md file.
• I have tested these changes locally (localhost:3000/api/streak?user=YOUR_USERNAME).
• I have run npm run format and npm run lint locally and resolved all errors (CI will fail otherwise).
• My commits follow the Conventional Commits format (e.g., feat(themes): ..., fix(calculate): ...).
• I have updated README.md if I added a new theme or URL parameter.
• I have starred the repo.
• I have made sure that i have only one commit to merge in this PR.
• The SVG output matches the CommitPulse "premium quality" aesthetic standard (no raw elements, smooth animations, correct fonts).
• (Recommended) I joined the CommitPulse Discord community for contributor discussions, mentorship, and faster PR support.

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[github-actions]

📦 Next.js Bundle Size Report (Gzipped Sizes)

✨ No significant bundle size changes detected.

📊 Summary of Totals

Category	PR Size	Base Size	Difference
Total JS	3433.75 KB	3433.75 KB	0 B
Total CSS	258.05 KB	258.05 KB	0 B

[Aamod007]

I reviewed the PR title/description, linked issue #4431, checks, and the diff before labeling.

Labels applied:

• level:intermediate: the new app/api/compare/route.theme-contrast.test.ts file is a fairly large 208-line route test suite covering multiple success and error branches.
• quality:clean: the test cases are organized by concern and the getFullDashboardData mock keeps the route behavior isolated.
• type:testing: the PR is dedicated test coverage for the compare route.
• type:design: the assertions are explicitly about theme contrast, style tokens, and client-hint-driven visual cohesion.

I’m leaving this as a neutral comment rather than approving because the repo checks are green but the PR still carries a failing Vercel status context. That looks like a deployment integration/auth issue rather than a code failure.

To unblock it, the Vercel GitHub integration for the repo/team needs to be re-authorized or the status needs to be marked non-blocking by maintainers. Once the Vercel context is green, this can be reviewed normally.

[Aamod007]

This test file is doing useful work for �pp/api/compare/route.theme-contrast.test.ts. The mocked theme paths, error-status coverage, and payload equality checks give the route a clear guardrail against theme-sensitive regressions.

[github-actions]

🎉 Congratulations @Rakshak05! Your PR has been successfully merged. 🚀

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