How to get the class of a method's return value in Ruby

Question

Here is a technical question for developers that want to validate their skills before a technical interview.
This question is written in french and need to be translated to english.
Use english for technical terms in the french version (example : "string" instead of "chaine de caractère".)

Double escape all quotes in result like this: //"
Give result as JSON.

Accepted Answer

f.some_method('something'){ |c| c.class } == String

Answer

f.some_method raises an exception

Answer

f.other_method raises an exception

Question from the Ruby (legacy) test

How to get the class of a method's return value in Ruby