Clameurs/modules/system/tests/cron_queue_test.module

<?php

/**
 * Implements hook_cron_queue_info().
 */
function cron_queue_test_cron_queue_info() {
  $queues['cron_queue_test_exception'] = array(
    'worker callback' => 'cron_queue_test_exception',
  );
  $queues['cron_queue_test_callback'] = array(
    'worker callback' => array('CronQueueTestCallbackClass', 'foo'),
  );

  return $queues;
}

function cron_queue_test_exception($item) {
  throw new Exception('That is not supposed to happen.');
}

class CronQueueTestCallbackClass {

  static public function foo() {
    // Do nothing.
  }

}