title: Rspec and rails: Problems while testing libraries in the lib directory
body: <p>I have some classes in the lib directory, and I want to test it. My class which I want to test looks like:</p>
  
  <pre><code>class StatAggregation
    class &lt;&lt; self
      def skills_rate(user_id)
        user_id = User.find_by_id(user_id)
        ...
      end
    end
  end
  </code></pre>
  
  <p>I created spec:</p>
  
  <pre><code>require File.expand_path(File.dirname(__FILE__) + '/../../spec_helper')
  
  describe StatAggregation do
    fixtures [
      :users
    ]
  
    describe 'skills_rate method' do
      it 'should work' do
        @user_id = 1
        @user = mock_model(User)
        User.should_receive(:find_by_id).with(@user_id).and_return(@user)    
        ...
        StatAggregation.skills_rate(@user_id)
      end
    end
  end
  </code></pre>
  
  <p>It works ok, but it doesn't show where appeared error:</p>
  
  <pre><code>1)
  ArgumentError in 'PxStatAggregation skills_rate method should work'
  wrong number of arguments (1 for 0)
  script/spec:10:
  
  Finished in 0.326331 seconds
  </code></pre>
  
  <p>How to get number of line where appeared error "wrong number of arguments (1 for 0)"?</p>