A spec for a filter

privacy_filter.rb

class PrivacyFilter
  class << self 
    def filter(controller)
      @controller = controller

      first_article?(controller) or administrator?(controller) or user?(controller)
    end
    
    def first_article?(controller)
      controller.params[:id] == 1
    end

    def administrator?(controller)
      controller.authenticate_administrator!
    end

    def user?(controller)
      controller.authenticate_user!
    end
  end
end

privacy_filter_spec.rb

require "app/models/privacy_filter"

describe PrivacyFilter do

  let(:controller) do
    stub(:params => {:id => 2},
         :authenticate_administrator! => false,
         :authenticate_user! => true)
  end

  it "allows access to the root article" do
    controller.stub(:params => {:id => 1})
    PrivacyFilter.filter(controller).should be_true
  end

  it "allows access for administrators" do
    controller.stub(:authenticate_administrator! => true)
    PrivacyFilter.filter(controller).should be_true
  end

  it "allows access to users" do
    controller.stub(:authenticate_user! => true)
    PrivacyFilter.filter(controller).should be_true
  end
end