.to.be.equal(5);
        Polymer.dom(s2).appendChild(document.createElement('div'));
        expect(s2.items.length).to.be.equal(5);
        s2.forceSynchronousItemUpdate();
        expect(s2.items.length).to.be.equal(6);
      });

      suite('`select()` and `selectIndex()`', function() {
        test('`select()` selects an item with the given value', function() {
          s2.select('item1');
          assert.equal(s2.selected, 'item1');

          s2.select('item3');
          assert.equal(s2.selected, 