Add comprehensive contract test suite (unit + fuzz tests) - Issue #39

[paulinaapeh8]

Summary

Closes #39: Suite de tests para contratos (unit + fuzz)

Implemented comprehensive unit and property-based test coverage for all three Soroban smart contracts with 110 total tests:

• staking_pool: 42 tests (23 unit + 19 fuzz-like property tests)
• vinculo_lending: 37 tests (21 unit + 16 fuzz-like property tests)
• vinculo_sbt: 31 tests (16 unit + 15 fuzz-like property tests)

Key Invariants Protected

Staking Pool

✅ Balance never goes negative
✅ Only valid months (1, 3, 6, 12) accepted
✅ Correct APY mapping (4%, 7%, 11%, 18%)
✅ Interest calculation: (principal × APY × months) / 1200
✅ Unlock time strictly monotonic with duration
✅ Stake info properly cleared after unstaking

Vinculo Lending

✅ Tier limits strictly increase (300M < 600M < 1.5B < 5B XLM)
✅ APY rates decrease with tier (12% > 8% > 5% > 4%)
✅ Loan amount never exceeds tier limit
✅ Total owed always ≥ principal
✅ Repayment correctly handled (partial, full, overpayment)

Vinculo SBT

✅ Tier values strictly in range 1-4
✅ Tier 0 is default/revoked state
✅ Only admin can mint/revoke (SBT non-transferable)
✅ Metadata (name, symbol) constant
✅ Tier immutability without operations

Implementation Details

Test Location

All tests are embedded in contract source files using Rust's #[cfg(test)] modules:

• Tests next to implementation for easy review
• Consistent naming: test_[category]_[specific_case]
• Property-based coverage with fuzz-like edge cases

Running Tests

# All contracts
./backend/contracts/run-tests.sh

# Individual contract
cd backend/contracts/staking_pool && cargo test --lib

# Specific test
cargo test --lib test_apy_mapping_1_month

Test Data & Reproducibility

• All amounts deterministic and reproducible
• Coverage ranges: 1 unit to i128::MAX/2
• No external dependencies or network calls
• Each test <1ms (total suite ~1s)

Files Changed

• backend/contracts/staking_pool/src/lib.rs - Added 42 tests
• backend/contracts/vinculo_lending/src/lib.rs - Added 37 tests
• backend/contracts/vinculo_sbt/src/lib.rs - Added 31 tests
• backend/contracts/TEST_SUITE.md - Comprehensive test documentation
• backend/contracts/README_TESTS.md - Quick start guide
• backend/contracts/run-tests.sh - Unified test runner script

Acceptance Criteria Met

✅ PR includes reproducible test commands
✅ Reviewer can run tests locally and verify results
✅ PR description states which invariants are tested
✅ Consistent test naming and setup across contracts
✅ Tests embedded next to implementation
✅ Both unit and property-based (fuzz) coverage
✅ Deterministic test setup and data

[vercel]

@paulinaapeh8 is attempting to deploy a commit to the alankcr1-6443's projects Team on Vercel.

A member of the Team first needs to authorize it.

[drips-wave]

@paulinaapeh8 Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits