Syntax suger for defining double.

doublet.rb

module Doublet
  def doublet(name, &block)
    let(name) { double.tap(&block) }
  end

  def doublet!(name, &block)
    let!(name) { double.tap(&block) }
  end
end

RSpec.configure do |config|
  config.extend Doublet
end

describe 'Doublet usage' do
  doublet!(:my_mock) {|my_mock| my_mock.should_receive(:do_something) }

  specify { my_mock.do_something }
end

最近こんなものを作ったところです！
http://rubygems.org/gems/rspec-something

この例だとこんな感じで書けます。

require 'rspec'
require 'rspec/something'

describe 'Doublet usage' do
  let(:my_mock) { something.do_something }

  specify { my_mock.do_something }
end