I tried postman and found it rather weird. What did not suit me: problems with remembering history - i'd expect the much labored-at settings and vars and options to be stored in the cloud and not vanish if I re-install the extension or use other machine. no custom cookies - that's a deal breaker.

I prefer the excellent Fiddler tool for manual fiddling, and yet have to find a good test-suit tool. Or write it myself...