title: Check that a specific radio button is checked
body: <p>I'm performing some tests on a form with radio buttons. I have a radio button that has the following identifiers: </p>
  
  <pre><code>&lt;input checked=​"checked" class=​"radio_buttons optional" id=​"rating_commute_8" name=​"rating[commute]​" type=​"radio" value=​"8"&gt;​
  </code></pre>
  
  <p>I'm trying to get it to pass the following test, but it is giving me the error <code>Failure/Error: within(:css, '#rating_commute_8').should be_checked LocalJumpError: no block given (yield)</code>: </p>
  
  <pre><code>  within(:css, '#rating_commute_8').should be_checked
  </code></pre>