vitrine.rb

class ProductsController < ApplicationController
  def index
    @products = Product.vitrine(34)
    respond_with @products
  end
end

class Product < ActiveRecord::Base
  def self.vitrine(limit)
    with_state(:published).limit(limit)
  end
end

describe Product do
  describe 'vitrine' do
    it 'returns published products in a given limit ' do
      published_product_1 = Factory.create(:product, :published => true)
      published_product_2 = Factory.create(:product, :published => true)
      published_product_3 = Factory.create(:product, :published => true)
      unpublished_product_4 = Factory.create(:product, :published => false)

      vitrine = Product.vitrine(2)

      vitrine.should have(2).item

      vitrine.should include published_product_1
      vitrine.should include published_product_2

      vitrine.should_not include unpublished_product_3
      vitrine.should_not include unpublished_product_4
    end    
  end
end