Testing an inbound webhook is annoying in a way that's out of proportion to the problem.

A provider — Stripe, GitHub, Shopify, whatever — will POST a JSON body to a URL you own. You need to see exactly what they send, and you need to send it again after you change your handler. Neither of those is hard. But the usual setup is:

Start a tunnel so the provider can reach your laptop

Paste the generated URL into the provider's dashboard

Trigger the event in their UI