Base installation with TestPage that hides Page

SiteTreeError.php

<?php

	class TestPage extends Page{

		private static $singular_name = 'Test Page';
		private static $plural_name = 'Test Pages';
		private static $description = 'A test page';
		private static $hide_ancestor = 'Page';

		private static $db = array();
		private static $has_one = array();
		private static $has_many = array();
		private static $many_many = array();
		private static $many_many_extraFields = array();
		private static $belongs_many_many = array();
		private static $defaults = array();

		public function getCMSFields(){
			$fields = parent::getCMSFields();



			$this->extend('updateCMSFields', $fields);

			return $fields;
		}

	}

	class TestPage_Controller extends Page_Controller{

		public function init(){
			parent::init();



		}

	}

/* PageUpdateTask that errors at SiteTree.php:1658 */
	class PageUpdateTask extends BuildTask{

		protected $title = 'Page Update Task';
		protected $description = 'A task to update Page to TestPage';

		protected $enabled = true;

		function run($request){
			$pages = Page::get();

			foreach($pages as $page){
				$page->ClassName = 'TestPage';
				$page->write();
				$page->doPublish();
			}

		}

	}

Here is the error from the BuildTask:

http://puu.sh/hSvgv/57c2e5f4b0.png