I have released my Json Api test tool Struktural:
https://github.com/kennycason/struktural, I hacked most of it together last week and will continue working on this project. My goal is for it to become a test tool like Airborne was with Ruby. I really enjoyed RSpec + Airborne for validating basic facts about API responses. It supports a native Kotlin/Java interface as well as Yaml backed spec tests. I have plenty of examples in the README. I would love feedback as to how to make this library more useful/better.
It serves three basic tests:
Assert Json Structure: A lightweight test to assert presence of fields
Assert Json Types: A middleweight test to assert presence of fields and their types
Assert Json Values: A heavyweight test to assert presence of fields and their values