Slight adjustment in requirement for json

[uNetworkingAB]

Your test is good because the requirements make it impossible to cheat with a simplified parser / hardcoded response. BUT - the requirements for JSON parsing is ambiguous.

If you change the rule from "Server MUST parse body to JSON and serialize back to string" to something like "Server must respond with the value from JSON key "hello", then you have a defined requirement that is never ambiguous in what it means to "parse json".

Because, to parse and serialize JSON is basically "no operation". But taking the "world" from key "hello" makes it defined.