I suppose we could be talking circles around eachother, but I'd say many of what you've suggested as manual tests could be codified into an automated test just as easily.
Manual: `curl localhost:8080 | jq .` or whatever, brings value once.
Automated: `assert.ValidJSON(req.Body)` is basically identical, but can be repeated over and over again
Manual: `curl localhost:8080 | jq .` or whatever, brings value once.
Automated: `assert.ValidJSON(req.Body)` is basically identical, but can be repeated over and over again