Testing standard input with RSpec

spec_helper.rb

...

module Helpers
  # Replace standard input with faked one StringIO. 
  def fake_stdin(*args)
    begin
      $stdin = StringIO.new
      $stdin.puts(args.shift) until args.empty?
      $stdin.rewind
      yield
    ensure
      $stdin = STDIN
    end
  end
end

...

RSpec.configure do |conf|
  conf.include(Helpers)
end

stdin_spec.rb

require "spec_helper"

describe "standard input" do 
  it "should receive `foobar`" do
    fake_stdin("foobar") do 
      input = gets.to_s.chomp.strip
      input.should == "foobar"
    end
  end
end

This is awesome, thank you!