 container = fixture('basic');
        var input = Polymer.dom(container).querySelector('#i');
        var line = Polymer.dom(container.root).querySelector('.underline');
        assert.isFalse(line.classList.contains('is-highlighted'), 'line is not highlighted when input is not focused');
        MockInteractions.focus(input);
        requestAnimationFrame(function() {
          assert.isTrue(line.classList.contains('is-highlighted'), 'line is highlighted when input is focused');
          done();
        