title: How to assert number of elements using Capybara with proper error message?
body: <p>I know that in Capybara, you can do something like this:</p>
  
  <pre><code>page.should have_css("ol li", :count =&gt; 2)
  </code></pre>
  
  <p>However, assuming that page has for instance only one matching element, the error is not very descriptive:</p>
  
  <pre><code>  1) initial page load shows greetings
   Failure/Error: page.should have_css("ol li", :count =&gt; 2)
   expected css "ol li" to return something
  </code></pre>
  
  <p>Instead of this rather obscure error message, is there a way to write the assertion in such way that error output would be something like 'When matching 'ol li', expected: 2, found: 1'. Obviously I could make a custom logic myself for such a behaviour - I'm asking is there a way to do this 'out of the box'?</p>
  
  <p>For what it's worth, I'm using Selenium driver and RSpec.</p>