The webhook test should send through the body of the last webhook that would have been, or was, fired. Or at least it should send through the same schema.
It's somewhat painful to test handling of the webhook when you need to wait for a job or workflow to complete to get the contents of a normal webhook.
Yes, I have a similar experience of webhook's unwieldy handling, hope to see more updates soon. https://eggycar.net
Thanks for this feedback Evan!