ure('custom');
        target = f.$.button;
        tooltip = f.$.buttonTooltip;
      });

      test('tooltip is shown when target is focused', function() {
        var actualTooltip = Polymer.dom(tooltip.root).querySelector('#tooltip');
        assert.isTrue(isHidden(actualTooltip));

        MockInteractions.focus(target);
        assert.isFalse(isHidden(actualTooltip));
      });

      test('tooltip is positioned correctly', function() {
        var actualTooltip = Polymer.dom(tooltip.root).querySelec