Implement custom assertions for balance changes

[adams813]

Description

This issue is to track the work for: Implement custom assertions for balance changes.

Guidelines for Contributors

1. Please review the repository's CONTRIBUTING.md.
2. Fork the repository and create a new feature branch.
3. Ensure that tests are added for any new functionality.
4. Run cargo test and cargo clippy locally before submitting a PR.
5. Reference this issue in your PR description.

[Osifowora]

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

​Hi maintainer, I would love to work on this issue. I can get started on it right away.

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

[yunus-dev-codecrafter]

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

Hi! I've carefully reviewed the entire task description and fully understand the requirements and expected outcome.
I have experience working on similar tasks and I'm confident I can complete this within about an hour. I'd be happy to take ownership of this issue and submit a clean, well-tested solution promptly.
If it's available, please assign it to me. Thank you!

ℹ️ Repo Maintainers: To accept this application, review their application or assign @yunus-dev-codecrafter to this issue.

[ekelemepraise-code]

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

GM GM Maintainer, pls can I work on this issue ? ETA - 12hrs

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

[drips-wave]

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

🧑‍💻 @ekelemepraise-code: 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 🌊