silverstripe-frameworktest/code/FrameworkTestSiteTreeExtension.php

<?php
class FrameworkTestSiteTreeExtension extends DataExtension {
	
	private static $has_one = array('RelationFieldsTestPage' => 'RelationFieldsTestPage');
	private static $belongs_many_many = array('RelationFieldsTestPages' => 'RelationFieldsTestPage');

}