title: Simple rspec test of initialize, include and class variable existance
body: <p>I am learning rspec right now and wanna test my ability class from "devise" which this code:</p>
  
  <pre><code>class Ability
    include CanCan::Ability
  
    def initialize(user)
  
      @user = user || User.new
  </code></pre>
  
  <p>my current rspec looks like this:</p>
  
  <pre><code>require 'spec_helper.rb'
  
  describe Ability do
  
    let(:user) { User.new }
    let(:ability) { Ability.new(user) }
  
    it 'should be an instance of Abiliy' do
      # expect(@user).to be_an_instance_of User # also works
      ability.should be_an_instance_of Ability
      # passes test
    end
  
    it "should include CanCan::Ability" do
      expect(:ability).to include(CanCan::Ability)
      # NoMethodError: undefined method `include?'
    end
  
    it 'should initialize with a User' do
     pending
    end
  
    it 'should have @user instance variable' do
      ability.user.should == User
      # NoMethodError: undefined method `user'
  
    end
  </code></pre>
  
  <p>can someone offer an example. I did a research but without success....</p>