Add test coverage asserting idempotent register/unregister and event payloads for pair lifecycle

[1nonlypiece]

Test pair lifecycle events and idempotency edges

Description

The existing suite in src/lib.rs covers basic register/unregister round-trips, but it never asserts the emitted events for the pair lifecycle (pair_reg, unreg, fee_set, liq_set, init) and never verifies edge behaviors like unregistering a never-registered pair, re-registering after unregister, or that unregister_pair leaves the configured fee untouched (the behavior its own doc comment claims). This issue adds event-assertion and lifecycle-edge coverage.

Requirements and context

• Repository scope: StableRoute-Org/Stableroute-contracts only.
• Use env.events().all() to assert the topic and data tuple emitted by init, register_pair, unregister_pair, set_pair_fee_bps, and set_pair_liquidity.
• Cover: unregister of a never-registered pair is a clean no-op, re-register after unregister works, and unregister_pair does NOT clear PairFeeBps (documenting the current behavior precisely).
• Use the existing setup_initialized helper; no production change expected unless a discrepancy is found.
• Assert exact event counts so a future extra/missing publish is caught.

Suggested execution

• Fork the repo and create a branch
• git checkout -b test/contracts-38-pair-lifecycle-event-tests
• Implement changes
  • Write code in: src/lib.rs — no production change expected (open a follow-up if a gap is found).
  • Write comprehensive tests in: src/lib.rs #[cfg(test)] mod test — the event-assertion and lifecycle-edge suite described above.
  • Add documentation: note the pair-lifecycle test matrix in README.md or docs/testing.md.
  • Include NatSpec-style doc comments (///) on any new test helper.
  • Validate security assumptions: events are emitted exactly once per state change with the documented payload.
• Test and commit

Test and commit

• Run cargo fmt --all -- --check, cargo build, and cargo test.
• Cover edge cases and failure paths: event topic/data per entrypoint, no-op unregister, re-register, fee survives unregister.
• Include the full cargo test output and a short security notes section in the PR description (threat model + mitigations).

Example commit message

test: cover pair lifecycle events and idempotency edges

Guidelines

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

Community & contribution rewards

• 💬 Join the StableRoute community on Discord for questions, reviews, and faster merges: https://discord.gg/37aCpusvx
• ⭐ 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.

[ekwe7]

I would love to work on this issue. I have experience building production ready applications and collaborating through GitHub workflows. I'll carefully analyze the current implementation, propose a reliable solution, and submit a well-tested PR. My focus is on clean code, maintainability, and timely delivery