testing: expand eip712 signing test fixtures and edge cases

[nanaf6203-bit]

Summary

src/utils/eip712/eip712Signing.ts has tests but is missing edge cases for typing of OptionalAll types, and no coverage for missing fields.

Affected area

src/utils/eip712/__tests__/eip712Signing.test.ts

Expected behaviour

Add fixtures and tests for empty signers, malformed payloads, and replay protection.

Acceptance criteria

• Coverage >90 %.

[gbengaeben]

@gbengaeben has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi Maintainer,

I’d love to work on this issue. I’ve reviewed the requirements and believe I can implement the solution according to the project’s guidelines and best practices.

If the issue is available, I’d be happy to take ownership and submit a PR for review.

Thank you for your consideration

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

[Kayce10]

@Kayce10 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hello Sir,

I came across your project and will love to have the opportunity to work on it

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Kayce10 to this issue.

[drips-wave]

Congratulations, @gbengaeben! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @gbengaeben: 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.

Warning

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

🌊 Happy Wave 🌊

[drips-wave]

This issue has been completed by @gbengaeben as part of the Stellar Wave Program's 6th Wave 🥳

😎 @gbengaeben: You earned 200 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here. You can also Leave a review to share your experience working on this issue.

🧑‍💻 Repo maintainers: How'd the contributor do? Leave a review to share your experience working with them.