someone.rb

class Someone
  class << self
    def say      
      $stdin.each_line do |line|
        $stdout << "someone says '#{line}' @ #{Time.now}"
      end
    end
  end
end

someone_spec.rb

require 'rubygems'
require 'rspec'
require 'otaku'
require 'cross-stub'
require File.join(File.dirname(__FILE__),'someone')

describe 'Someone' do

  before do
    # Cross-process stubbing if required (initializes the stubs cache)
    CrossStub.setup :file => '/tmp/crosstub.cache'

    # Wrap & execute stdin/stdout manipulation in another process (using otaku service)
    Otaku.start do |data|
      begin

        # Need to explicitely require the definition for Someone (cos this block actually
        # runs in another process)
        require File.join(File.dirname(__FILE__),'someone')

        # Replace stdout & stdin with instances of StringIO
        $o_stdout, $o_stdin = $stdout, $stdin
        $stdout, $stdin = StringIO.new, StringIO.new
        $stdin << data
        $stdin.rewind

        # Cross-process stubbing if required (refreshes the stubs cache)
        require 'cross-stub'
        CrossStub.refresh :file => '/tmp/crosstub.cache'

        # Running the to-be-tested method
        Someone.say

        # Grab the stdout dump
        $stdout.rewind
        $stdout.readlines.join

      ensure
        # Ensures stdout & stdin are reverted back to the originals
        $stdout, $stdin = $o_stdout, $o_stdin
      end
    end
  end

  after do
    Otaku.stop
    CrossStub.clear
  end

  it 'should say something' do
    Otaku.process('hello').should match(/^someone says 'hello'/)
  end

  it 'should say something else' do
    Time.xstub(:now => '2012')
    Otaku.process('hello').should == "someone says 'hello' @ 2012"
  end

end