title: Assert presence of a css class when the element is already selected with CasperJS
body: <p>Is there a way to assert the presence or absence of a css class given I have located the element through another class applied to it?</p>
  
  <p>Here is a sample dom structure - </p>
  
  <pre><code>&lt;div class="large-20 small-20 small-centered large-centered columns"&gt;
      &lt;div class="row"&gt;
        &lt;div class="divider1"&gt;&lt;/div&gt;
        &lt;input name="options" type="checkbox" value="2" class="selectable-options grid-value" /&gt;
      &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>where the 'selectable-options' is the class that gets added to the element based on some conditions, and I would like to assert its presence or absence based on the workflow I am testing.
  I use xpath to reach this element.
  How do I achieve this? </p>