text: /* global circles */
  QUnit.test('Element Z index', function (assert) {
  
      function getIndex(element) {
          var i = 0,
              nodes = element.parentNode.childNodes;
          while (i < nodes.length) {
              if (nodes[i] === element) {
                  return i;
              }
              i++;
          }
      }
  
  
      assert.strictEqual(
          typeof getIndex(circles[1].element),
          'number',
          'Yellow is there'
      );
      assert.strictEqual(
          typeof getIndex(circles[2].element),
          'number',
          'Blue is there'
      );
      assert.strictEqual(
          getIndex(circles[1].element) > getIndex(circles[2].element),
          true,
          'Yellow in front of blue'
      );
  
      circles[1].attr({
          zIndex: 3
      });
  
      assert.strictEqual(
          getIndex(circles[1].element) < getIndex(circles[2].element),
          true,
          'Yellow behind blue'
      );
  
      // ... and back again
      circles[1].attr({
          zIndex: 6
      });
  
      assert.strictEqual(
          getIndex(circles[1].element) > getIndex(circles[2].element),
          true,
          'Yellow in front of blue'
      );
  
  });