Webhook replay can reproduce a useful failure, but replaying an event is still an action. A handler may update records, queue emails, or call another service. Treat the destination and side effects as part of the test setup.
Start with a controlled environment and a known fixture. Keep production listener data and credentials out of the test where they are not needed.
Preserve the scenario, not just the JSON
Record the relevant method, headers, raw body, event identity, and expected processing result according to your provider's test tools. A payload copied into a different parser path may miss the middleware bug you are trying to reproduce.
Use a dedicated test secret or the provider's documented simulator flow. Do not disable signature verification in a publicly reachable production handler just to make a replay convenient.
Before sending, list possible side effects and how you will observe them. A successful HTTP response does not prove that the database update, deduplication rule, and downstream job all behaved correctly.
Replay a small sequence
Send one valid event, repeat it, and then send a deliberately modified invalid fixture. The valid duplicate should follow your duplicate-handling rule. The modified request should fail verification and leave business state unchanged.
If the original incident involved reversed delivery or a restart, include that condition rather than testing only a normal event. Keep the expected outcome written down before inspecting the result.
After the test, remove exact fixture records and temporary endpoints that you created. Preserve the non-secret result and the steps needed to reproduce it. That gives the next investigation a useful starting point without leaving a second event path in production.