A comment says order cancellation is idempotent. What is the best next check?

A comment says order cancellation is idempotent. What is the best next check?

1. Call cancellation twice on the same paid order and assert the state plus refund and event counts
2. Search for the word idempotent in more comments
3. Confirm the cancellation function returns the same object type
4. Ask the model to restate why idempotency is desirable