Add zero-balance key read tests

[Chucks1093]

Summary

Add focused tests for zero-balance key read behavior.

Scope

• add tests for zero-balance read cases
• keep the tests small and readable
• verify expected return behavior clearly

Acceptance Criteria

• zero-balance read paths are covered by tests
• expected outputs are asserted clearly
• tests stay focused on read behavior only

Contributor note: comment on the issue first and reach out in Telegram for updates or coordination: https://t.me/accesslayerorg

[Kaycee276]

@Kaycee276 has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

I'd like to work on this issue because writing focused, well-scoped tests for edge case read behavior — particularly zero-balance paths — is something I approach carefully, making sure assertions are precise and tests remain readable without scope creep into write or mutation behavior. I have experience writing targeted unit and integration tests for smart contracts, including boundary conditions like zero-value reads, and I'm comfortable keeping test suites small and expressive without over-engineering them.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Kaycee276 to this issue.

[Abidoyesimze]

@Abidoyesimze has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

Hi Maintainer, i'd like to work on this issue

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

[drips-wave]

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

🧑‍💻 @Abidoyesimze: 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 @Abidoyesimze as part of the Stellar Wave Program's 3rd Wave 🥳

😎 @Abidoyesimze: 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.