title: What does sinon's stub.yields do?
body: <p>The documentation for sinon says stub.yields does this:</p>
  
  <blockquote>
    <p>stub.yields([arg1, arg2, ...]) Similar to callsArg.</p>
    
    <p>Causes the stub to <strong>call the first callback it receives</strong> with the
    provided arguments (if any).</p>
    
    <p>If a method accepts more than one callback, you need to use
    yieldsRight to call the last callback or callsArg to have the stub
    invoke other callbacks than the first or last one.</p>
  </blockquote>
  
  <p>I've read this a few times and can't understand what it is trying to communicate.  I find the bold part to be especially confusing.  </p>
  
  <p>What would help me is an explanation that's more detailed than this and an example or two showing how to use <code>yields</code> (the documentation does not provide that).  </p>