tests/mocks/database/drivers/pdo.php

<?php

class Mock_Database_Drivers_PDO extends Mock_Database_DB_Driver {

	/**
	 * Instantiate the database driver
	 *
	 * @param	string	DB Driver class name
	 * @param	array	DB configuration to set
	 * @return	void
	 */
	public function __construct($config = array())
	{
		parent::__construct('CI_DB_pdo_driver', $config);
	}
}