[TESTING & QA] Write unit tests for carbon_credit contract business logic

[dev-fatima-24]

Priority: high

Description

The carbon_credit contract has 10 tests but is missing coverage for: minting credits for a suspended project, retiring more credits than owned, and the serial number conflict detection. These are the most critical business rules in the entire system.

Acceptance Criteria

• Test for minting credits on a suspended project returns ProjectSuspended
• Test for retiring more credits than owned returns InsufficientCredits
• Test for serial number conflict detection returns SerialNumberConflict
• Test for retiring already-retired credits returns AlreadyRetired
• Test for zero amount retirement returns ZeroAmountNotAllowed

[raphael-01-visual]

@raphael-01-visual has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Can I work on this issue ? ETA - 12hrs

ℹ️ Repo Maintainers: To accept this application, review their application or assign @raphael-01-visual to this issue.

[drips-wave]

Congratulations, @raphael-01-visual! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

🧑‍💻 @raphael-01-visual: 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

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