Add tests for the agent allowlist enforcement path in record_usage

[mikewheeleer]

Test the agent allowlist gate end to end

Description

The allowlist logic in record_usage (and set_allowlist_enabled, set_agent_allowed, is_agent_allowed) in contracts/escrow/src/lib.rs has no coverage in contracts/escrow/src/test.rs — no test asserts that an off-allowlist agent is rejected with AgentNotAllowed (#10) or that disabling the gate restores access. This issue closes that gap with focused tests.

Requirements and context

• Repository scope: Agentpay-Org/Agentpay-contracts only.
• Cover: allowlist disabled (default) allows any agent; enabled + agent not listed → panic #10; enabled + agent allowed → succeeds; allowed then revoked → rejected again.
• Assert is_allowlist_enabled and is_agent_allowed round-trips.
• Use #[should_panic(expected = "Error(Contract, #10)")] matching the existing test conventions.
• Do not modify contract logic; this is a test-only change unless a genuine bug surfaces (then file separately).

Suggested execution

• Fork the repo and create a branch
• git checkout -b test/contracts-16-allowlist-tests
• Implement changes
  • Write code in: contracts/escrow/src/lib.rs — no changes expected; only touch if a bug is found.
  • Write comprehensive tests in: contracts/escrow/src/test.rs — the allowlist scenarios above.
  • Add documentation: note the covered behaviour in the test module header comment.
  • Include NatSpec-style doc comments (///) where helper functions are added.
  • Validate security: tests prove the gate cannot be bypassed.
• Test and commit

Test and commit

• Run cargo fmt --all -- --check, cargo build, and cargo test.
• Cover edge cases: toggling the gate while usage exists, multiple agents with mixed status.
• Include the full cargo test output and a short security notes section in the PR description.

Example commit message

test: cover agent allowlist enforcement in record_usage

Guidelines

• Minimum 95 percent test coverage for impacted modules.
• Clear, reviewer-focused documentation.
• Timeframe: 96 hours.

Community & contribution rewards

• 💬 Join the AgentPay community on Discord for questions, reviews, and faster merges: https://discord.gg/eXvRKkgcv
• ⭐ This is a GrantFox OSS / Official Campaign task and may be rewarded. When your PR is merged you'll be prompted to rate the project — if this issue and the maintainers helped you ship, we'd be grateful for a 5-star rating. Clear questions in Discord and tidy, well-tested PRs are the fastest path to a merge and a reward.

[greatest0fallt1me]

Hello Maintainers 👋,
I’m interested in picking up this issue and contributing to the project.
I have solid experience working across both frontend and blockchain layers, including building user interfaces with Next.js and developing Stellar smart contracts using Rust (Soroban). I’m familiar with translating Figma designs into pixel-accurate UIs, handling wallet integrations, and writing efficient, well-tested contract logic.
I focus on writing clean, maintainable code, following repository standards, and keeping communication transparent throughout the development process. I can start immediately and complete the work within the expected timeframe.
Excited to collaborate and add value to the project 🚀
Thank you!

[grantfox-oss]

🦊 GrantFox — @greatest0fallt1me 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 #16)
2. Your PR will be reviewed by the Agentpay-Org maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign campaign!

@greatest0fallt1me's PR #74 was approved and merged by @mikewheeleer.

🏆 @greatest0fallt1me: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (293 total points). Track your full progress on GrantFox.

👏 Great work, @greatest0fallt1me! Keep contributing to Agentpay-Org.