Add invariant and fuzz tests for MembershipNFT

[Lakes41]

Summary

Strengthen smart contract confidence by adding invariant and fuzz tests for membership minting, renewal, suspension, and ownership behaviour.

Current Behaviour

The contract has direct tests for expected flows, but complex sequences and edge cases may not be covered systematically.

Expected Behaviour

The contract test suite should verify important invariants across many generated inputs and state transitions.

Suggested Implementation

Add Foundry fuzz tests and invariant tests around token ownership, wallet-to-token mapping, expiry updates, suspension state, and access control. Include handlers where needed to model realistic sequences of mint, renew, suspend, and transfer attempts.

Files or Areas Likely Affected

• contracts/src/MembershipNFT.sol
• contracts/test/MembershipNFT.t.sol
• contracts/test/
• contracts/foundry.toml

Acceptance Criteria

• Fuzz tests cover minting with varied wallets and expiry values
• Invariants ensure each wallet maps to at most one active membership token
• Invariants ensure suspended memberships cannot be treated as active
• Access-controlled functions are tested with authorised and unauthorised callers
• Edge cases around zero addresses and invalid expiry values are covered
• Contract tests run successfully through the existing Foundry workflow

Additional Notes

If the contract intentionally permits transfers, invariants should reflect the intended wallet-to-token behaviour after transfer.

[coderolisa]

Hello Maintainer,
I'd like to work on this issue. I've reviewed the requirements and can complete the implementation as specified.
Please assign it to me. Thank you!

[OlaGreat]

I'd like to take this on.

I'm a software engineer with experience in blockchain, backend systems, and open-source contribution. I've reviewed the issue and I'm confident I can deliver a clean implementation with tests covering the acceptance criteria. Happy to follow the project's existing conventions.

[grantfox-oss]

🦊 GrantFox — @coderolisa has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #21)
2. Your PR will be reviewed by the Adamantine-guild maintainers

Good luck! Track your progress on GrantFox.