title: multiple field validation with jquery validate plugin
body: <p>I have two input checkboxes as below:</p>
  
  <pre><code>&lt;input type="checkbox" value="1" name="items[test1]" id="items_test1"&gt;
  &lt;input type="checkbox" value="1" name="items[test2]" id="items_test2"&gt;
  </code></pre>
  
  <p>I want atleast one of them to be checked.
  For that I added jquery validate plugin code as below:</p>
  
  <pre><code> $.validator.addMethod("checkTest", function(value) {
      return false; // return false just to check whether it triggers error
  }, 'Please check atleast one');
  
   $(document).ready(function() {
       $("form").validate({
           groups: {
              checkTest: 'items[test1] items[test2]'
           },
           errorPlacement: function(error, element) {
                console.log(error);
       });
   });
  </code></pre>
  
  <p>This check is nevered triggered. What am I doing wrong?</p>