[mordabdul1]

Summary

Closes #80.

Adds test_collect_fees_double_invocation_never_double_collects to src/test.rs: collect_fees(asset) is invoked twice in immediate succession (same ledger — the env's sequence number is never advanced), asserting the first call pays the full accrual and zeroes fees_accrued, and the second fails with Error::NoFeesToCollect — never re-collecting the same amount. The test further proves post-collection accruals form a fresh balance (exactly the new amount is collectable, no residue) and that the guarantee holds again after re-accrual.

Checks-effects-interactions review (no gap found)

collect_fees in src/lib.rs already follows CEI ordering, so no reorder was needed:

1. Checks — admin auth, then a non-zero accrual (else NoFeesToCollect).
2. Effects — fees_accrued is zeroed; this is the function's only state mutation.
3. Interactions — there are none. No SEP-41 token transfer or any other cross-contract call exists on this path: accrued fees are internal accounting, and the function just emits an event and returns the amount.

With no external call frame anywhere in the function, there is nothing for a malicious token to reenter through — and the Soroban host additionally forbids contract reentrancy outright, so the guarantee is defense in depth. Should a real token payout ever be added to this path, the accrual is already zeroed before the point where such a transfer would go, and this regression test would pin the observable behavior.

Testing

Full suite: 154 passed, 0 failed. cargo fmt --check clean.

Incidental

Bumps ethnum 1.5.2 → 1.5.3 in Cargo.lock (1.5.2 fails to compile on recent rustc, E0512). Same patch bump as #173/#174/#175/#177; merges cleanly in any order.