xh and tiny shell scripts.

Example: sign-up-forbidden-username.req

#!/bin/bash
xh POST http://0.0.0.0:2884/sign-up usename=admin password=pw

to run ./sign-up-forbidden-username.req

This returns 403 and "Username is unavailable"

https://github.com/ducaale/xh

xh is a rust implementation of httpie. They're going for full parity, and works really well for what I need it for so far You can also read input from a file. Which IMO makes GUI API testing seem silly.