registerClassTransformation: function(Transformation, className) {
         var thisClassTransformations = (this.classTransformations[className] = this.classTransformations[className] || {});
-        thisClassTransformations[Transformation.prototype.name] = function(args) {
+        thisClassTransformations[Transformation.prototype.name] = function() {
             var nodeInstance = this;
+            var args = Array.prototype.slice.call(arguments, 0);
             return nodeInstance.transform(Transformation, args);
         };
     },
 
 
 return {
-    WLXMLDocumentFromXML: function(xml, options) {
+    WLXMLDocumentFromXML: function(xml, options, Factory) {
         options = _.extend({wlxmlClasses: wlxmlClasses}, options);
-        return new WLXMLDocument(xml, options);
+        Factory = Factory || WLXMLDocument;
+        return new Factory(xml, options);
     },
 
     WLXMLElementNodeFromXML: function(xml) {
         return this.WLXMLDocumentFromXML(xml).root;
-    }
+    },
+
+    WLXMLDocument: WLXMLDocument
 };
 
 });
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