title: How do I check if element exists with Mocha Chai Sinon?
body: <p>I would like to know how can I check if an element on the UI exists by id or class. I'm using teaspoon-mocha, Sinon, and chai. </p>
  
  <p>I tried next but it doesn't work:</p>
  
  <pre><code>expect($('my-id')).to.be.true;
  </code></pre>