d', onIronItemsChanged);
            done();
          });
        });

        test('cause iron-items-changed to fire', function(done) {
          var newItem = document.createElement('div');
          var changeCount = 0;

          newItem.id = 'item999';

          s2.addEventListener('iron-items-changed', function(event) {
            changeCount++;
            var mutation = event.detail;
            assert.notEqual(mutation, undefined);
            assert.notEqual(mutation.addedNodes, undefined);
   