Comprehensive Tests for carbon credit registry contract

[FrankiePower]

Pull Request: Comprehensive Tests for Carbon Credit Registry

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📌 Description

This PR modularizes the test suite for the carbon-credit-registry contract, organizing tests into focused modules and adding comprehensive edge case coverage. The implementation creates 31 comprehensive tests across three modules (issuance, trading, retirement), with reusable test utilities for improved maintainability and compliance verification.

closes #59

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📌 Type of Change

• Documentation (updates to docs or comments)
• Bug fix (non-breaking change fixing issues)
• Enhancement (adds comprehensive test coverage and organization)
• Breaking change

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🎯 Motivation and Context

This PR addresses the need for comprehensive test coverage for the carbon credit registry system. The previous implementation had an empty test.rs file with no tests. This implementation provides:

• Test Organization: Tests are now grouped by credit lifecycle (issuance, trading, retirement)
• Compliance Coverage: Tests verify carbon credit standards and audit requirements
• Edge Case Coverage: 9 edge case tests covering invalid operations and boundary conditions
• Maintainability: Reusable test utilities reduce code duplication
• Auditability: Clear test structure ensures carbon credit compliance verification

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🛠️ How to Test the Changes

1. Navigate to contract directory:

   cd soroban/contracts/carbon-credit-registry

2. Run all tests:

   cargo test

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✅ Checklist Before Merging

• 🧪 I have tested the code and all 31 tests pass.
• 🎨 My changes follow the project's coding style and modular test patterns.
• 📖 Test utilities are well-documented with clear function purposes.
• ⚠️ No new errors were introduced (only existing warnings remain).
• 🔍 I have reviewed and approved my own code before submitting.
• 📊 Test coverage increased from 0 to 31 tests.
• 🎯 All core requirements from task objectives are covered.
• 🔧 All edge case tests now passing (fixed unique credit ID generation).

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📝 Notes

• Unique Credit ID Generation: Implemented timestamp-based uniqueness in test utilities to ensure each issued credit receives a unique ID. Both issue_test_credit() and issue_credit_with_params() now embed the current ledger timestamp in verification hashes and increment the timestamp after each issuance.

• Compliance Ready: All tests verify carbon credit standards compliance with proper audit logging through credit history tracking.

• Integration Note: Tests are designed to validate integration with renewable-energy-certificate-tracker for renewable energy offsets (as mentioned in requirements).

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Conclusion

This PR successfully implements comprehensive test coverage for the carbon-credit-registry contract, providing robust verification of credit issuance, trading, and retirement flows. The modular structure ensures compliant and transparent carbon credit management through well-organized tests that verify data integrity, authorization, and audit logging at every stage of the credit lifecycle.

[FrankiePower]

@salazarsebas this PR is ready to be reviewed and merged

[salazarsebas]

LGTM