Now that you've configured your local server, you might be interested in pushing your code to the limits. To that end, GitHub's webhooks view provides some tooling for testing your deployed payloads.
Every webhook has its own "Recent Deliveries" section, which lists, at a glance whether a delivery was successful (green check) or failed (red x). You can also identify when each delivery was attempted.
GitHub AE keeps a log of each webhook delivery for 8 days.
By expanding an individual delivery, you'll be able to witness precisely what information GitHub is attempting to send to your server. This includes both the HTTP Request and Response.
The webhook delivery view provides information on which Headers were sent by GitHub. It also includes details about the JSON payload.
The response tab lists how your server replied once it received the payload from GitHub. This includes the status code, the headers, and any additional data within the response body.