ZK-062: Add fuzz and property tests for note serialization, witness encoding, and Merkle paths

[ANAVHEOBA]

Wave: PrivacyLayer ZK Wave 1
Issue Key: ZK-062
Area: testing
Priority: Medium
Drips Complexity: High

Summary

Complement fixed fixtures with fuzz and property tests over the most failure-prone encoding and tree-handling code.

Relevant Code

• sdk/src/note.ts
• sdk/src/proof.ts
• sdk/src/merkle.ts

Scope

• Fuzz note import/export, witness serialization, and Merkle path generation with seeded randomness.
• Promote minimal reproductions from failing fuzz cases into fixed regressions.
• Focus on deterministic coverage that can run in CI.

Acceptance Criteria

• Fuzz or property tests cover note parsing, witness encoding, and Merkle path logic.
• Failures are reproducible from saved seeds or reduced cases.
• The suite is stable enough for automated runs.

Out of Scope

• Soroban contract changes
• Frontend and wallet UI work

Dependencies

• ZK-015
• ZK-028
• ZK-055

References

• sdk/src/note.ts
• sdk/src/proof.ts
• sdk/src/merkle.ts

[Jumongweb]

@Jumongweb has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

Hi maintainer, i will like to solve this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Jumongweb to this issue.

[AugustineAniobasi]

@AugustineAniobasi has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

I would like to apply for this issue...

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[drips-wave]

Congratulations, @AugustineAniobasi! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on April 29, 2026.

🧑‍💻 @AugustineAniobasi: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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[laolaoqi]

I can take on this fuzz and property testing task (ZK-062).

What I can do:

• Implement seeded-randomness fuzz tests for note serialization (import/export), witness encoding, and Merkle path generation
• Write property-based tests that verify round-trip correctness and encoding invariants
• Promote any failing fuzz cases into fixed regression tests
• Ensure the suite is deterministic and CI-stable per the acceptance criteria

Timeline: PR ready within 5-7 days of assignment.

Technical fit: I have strong experience writing fuzz/property tests in TypeScript for cryptographic and encoding-heavy codebases. Familiar with deterministic testing patterns, seed-based reproducibility, and CI integration.

Payment address: 0x6c21794E27C34E93cd0049918d04Da58FC72595c