public function perform()
  {
    $this->_installManagers();

    $this->response->write("Flushing full page cache...");

    $full_cache_mgr = new FullPageCacheManager();
    $full_cache_mgr->flush();

    $this->response->write("done\n");

    $this->response->write("Flushing partial page cache...");

    $partial_cache_mgr = new PartialPageCacheManager();
    $partial_cache_mgr->flush();

    $this->response->write("done\n");

    $this->response->write("Flushing images cache...");

    $image_cache_mgr = new ImageCacheManager();
    $image_cache_mgr->flush();

    $this->response->write("done\n");
  }
  function testIsNotCacheableNoUri()
  {
    $cache_manager = new ImageCacheManager();

    $this->assertFalse($cache_manager->isCacheable());
  }