title: How to write xpath for a button with class attribute?
body: <p>I have just started working on Selenium-Ruby . 
  My html looks something like this-</p>
  
  <pre><code>&lt;button class="check column btn btn-invisible"&gt;
     &lt;i class="icon-column-p"&gt;&lt;/i&gt;
      "Check Column"
  &lt;/button&gt;
  </code></pre>
  
  <p>I want to click on the button, what would be the best xpath to access it?</p>
  
  <p>Thanks!</p>