Not able to parse this QString(in XML format) using XQuery

I want to parse the following xml (get the type ids and the test output and so on)stored in the QString expected_xml using XQuery,

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE TEST_XML>
<TEST TEST_VERSION="14">
 <TEST_TYPES>
  <TEST_TYPE ID="0"/>
  <TEST_TYPE ID="1"/>
 </TEST_TYPES>
 <TEST_QUERY_LIST PROP="0">
  <TEST_QUERY_FILE>"C:/Files/File.txt"</TEST_QUERY_FILE>
 </TEST_QUERY_LIST>
 <TEST_OUTPUT>
  <FILE PATH="C:/Files/File2.txt" TEST_TYPE_ID_REF="1">
   <USED_BY TEST_PATH="C:/Files/File2.txt" ALIAS="thisData"/>
  </FILE>
 </TEST_OUTPUT>
</TEST>

I use the following code to get the Ids for example, but this does not give me nothing. Do I miss anything very obvious ?

   //Test Parsing
   QByteArray xmlByteArry;
   QBuffer device(&xmlByteArry);
   device.setData(expected_xml.toUtf8());
   device.open(QIODevice::ReadOnly);

   QXmlQuery query;
   query.bindVariable("xmlByteArry", &device);
   query.setQuery("doc($xmlByteArry)//TEST/TEST_TYPES");

   if(query.isValid())
   {
      QStringList values;
      query.evaluateTo(&values);
      qDebug() << values;
   }

Solution

If you need the Id's, your Query is wrong. It should be:

    query.setQuery("doc($xmlByteArry)//TEST/TEST_TYPES/TEST_TYPE/@ID");

This Query returns the value of the Attributes.

Additional Info: If you have Errors in your Xml Query you can set a MessageHandler to read the Errors:

class MessageHandler: public QAbstractMessageHandler
{
    virtual void handleMessage(QtMsgType type,
        const QString &description,
        const QUrl &identifier,
        const QSourceLocation &sourceLocation)
    {
        qDebug() << QString("Xml Query Error: %1 at Line: %2 Character:")
            .arg(description).arg(sourceLocation.line()).arg(sourceLocation.column());
    }
};

Here is a small Example that reads the Attribute ID to a StringList:

bool test7::test()
{
    QByteArray xmlByteArry;
    QBuffer device(&xmlByteArry);
    device.setData(XmlTree().toUtf8());
    device.open(QIODevice::ReadOnly);

    QXmlQuery query;
    query.setMessageHandler(new MessageHandler());
    query.bindVariable("xmlByteArry", &device);
    query.setQuery("doc($xmlByteArry)//TEST/TEST_TYPES/TEST_TYPE/@ID");

    QStringList values;
    if(query.isValid())
    {
        QXmlResultItems result;
        query.evaluateTo(&result);

        QXmlItem XmlItem(result.next());

        while (!XmlItem.isNull()) 
        {
            if (XmlItem.isNode()) 
            {
                QXmlNodeModelIndex Index = XmlItem.toNodeModelIndex();
                values.append(Index.stringValue());
            }

            XmlItem = result.next();
        }
    }

    return true;
}

For more Information read the Qt XQuery Documentation: here

UPDATE: You can get the TESTPATH and PATH for a ID with the following query:

query.setQuery("for $x in doc($xmlByteArry)//TEST/TEST_OUTPUT/FILE"
        " return if($x/@TEST_TYPE_ID_REF = 1) "
        " then ($x/USED_BY/@TEST_PATH, $x/@PATH ) "
        " else ()");

Set the ID Value programmatically.