title: sinon.js verify mock method's arguments with callback
body: <p>Is it possible to verify arguments with a callback. I'm thinking something like this:</p>
  
  <pre><code>var spy = sinon.spy(someObject, "method");
  
  //json is an object with like 10 properties
  spy.withArgs(function(json){
    return 'undefined' !== typeof json.importantProp1 &amp;&amp; 'undefined' !== typeof json.importantProp2;
  });
  </code></pre>