Capture stdout example.

capture_stdout.rb

require 'stringio'

module Capture
  def self.stdout &block
    $stdout = captured_stdout = StringIO.new
    block.call
    captured_stdout
  ensure
    $stdout = STDOUT
    block.call
  end
end

captured = Capture.stdout { puts 'toast!' }
#=> #<StringIO:0x007fe0d3adbdb0>

captured.string
#=> "toast!\n"