code: function (testObject){
                  var node = new TestNode(testObject);
                  if (this.firstChild === null){
                      this.firstChild = this.lastChild = node;
                  } else {
                      this.lastChild.next = node;
                      this.lastChild = node;
                  }
                  node.parent = this;
                  return node;
              }
docs: Appends a new test object (TestSuite, TestCase, or test function name) as a child
  of this node.
  @param {Variant} testObject A TestSuite, TestCase, or the name of a test function.
  @return {Void}