There is a great tool rustdoc (currently used by cargo) to test examples of documentation comments in Rust. Does rdoc or yard give us something similar in Ruby?
Well, there few examples of doctest tool in Ruby, and the most fresh one (for now) is yard-doctest:
Meet YARD::Doctest - simple and magical gem, which automatically parses your @example tags and turn them into tests!
Probably no so powerful as rustdoc, but it does what it needs to.