Sample spec for https://twitter.com/tatzyr/status/615834332263899137

foo_spec.rb

require 'spec_helper'

class Foo
  def self.bar(*args)
    puts "foo"
    "bar"
  end
end

describe Foo do
  example do
    ret = ""
    expect{ret = Foo.bar}.to output("foo\n").to_stdout
    expect(ret).to eq "bar"
  end
end