test: add unit tests for src/secrets.ts

[doitrous]

Adds test/secrets.test.ts covering the three exports of src/secrets.ts:

• secretEquals: matching strings, non-matching, empty, unicode, different lengths
• deriveSigningKey: returns a usable HMAC key, caches same material, different material → different key
• hmacHex: 64-char hex output, determinism, distinct messages → distinct digests

12 tests, all pass under bun test.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Tests
  • Added coverage for secret comparison, signing-key derivation, and HMAC digest generation.
  • Added checks for matching and non-matching secrets, empty and Unicode inputs, deterministic results, key reuse, and distinct outputs for different inputs.
  • Verified HMAC signatures and hexadecimal digests have the expected formats and lengths.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: fdb7d9c6-3600-405a-93f8-4f6382a6ae05

📥 Commits

Reviewing files that changed from the base of the PR and between 5c241af and 6a1895c.

📒 Files selected for processing (1)

• test/secrets.test.ts

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📝 Walkthrough

Walkthrough

The pull request adds test/secrets.test.ts. The tests cover secretEquals, deriveSigningKey, and hmacHex, including comparison cases, key caching, signature differences, and hexadecimal digest output.

Changes

Secrets module tests

Layer / File(s)	Summary
Secrets behavior validation test/secrets.test.ts	Adds tests for matching, non-matching, different-length, empty, and Unicode secrets. Tests verify HMAC key usability, cached promise reuse, distinct outputs for different materials, and deterministic 64-character lowercase hexadecimal digests.

Priority: ⬇️ Low

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

Change: Other

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: adding unit tests for src/secrets.ts.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 1…
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.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create a new PR

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