title: RSpec lazy subject
body: <p>When testing class methods, I don't need an instance to be created automatically. Is an implicit subject created automatically, or only when referenced?</p>
  
  <pre><code>describe MyClass do
  
    it 'uses implicit subject' do
      subject.my_method.should be_true
    end
  
    it 'does not create a subject' do
      MyClass.works?.should be_true
      # subject should not have been created
    end
  end
  </code></pre>