XML : Adding A Node To A Nodelist Using XmlParser In Groovy

When I add a Node to a NodeList using the XmlParser in Groovy, the NodeList does not appear to reflect the change. Here is the code that I'm testing with in the GroovyConsole. If you run this code, you should see the output "ADD FAILED" followed by a dump of the three elements of the NodeList. I've also tried the same thing with XmlSlurper, but switched to XmlParser when I read that the DOM in XmlSluper is basically immutable and that changes only get applied during serialize. But with XmlParser, should this work?

  def xml = '''  <site id='myCoolSite'>    <pages/>    <templates/>    <properties>      <property name='good' value='true'/>      <property name='nice' value='true'/>      <property name='expensive' value='false'/>    </properties>    <stuff/>  </site>    '''      site = new XmlParser().parseText( xml )  assert site != null    assert site.properties.property instanceof NodeList  assert site.properties.property.size() == 3    def newNode = new Node(null, "property", [name: "foo", value: "bar"] )    site.properties.property.add( 0, newNode )    def foo = site.properties.property.find { it.@name == "foo" }    if ( foo == null ) {      println "ADD FAILED. Here are the only properties found: "      site.properties.property.each { println "${it.@name}=${it.@value}" }   }  else {      println "SUCCESS"  }