public function testPersistentConnectionCreation()
	{
		/** @var \Memcached $instance */
		$instance = MemcachedCache::createConnection("memcached://localhost", ['persistent_id' => 'persistent']);
		$this->assertCount(1, $instance->getServerList());

		$instance = MemcachedCache::createConnection("memcached://localhost", ['persistent_id' => 'persistent']);
		$this->assertCount(1, $instance->getServerList()); // fail here. 

		// disabling previous assert leads to segfault due libmemcached-1.0.18 bug
		$instance = MemcachedCache::createConnection("memcached://localhost", ['persistent_id' => 'persistent']);
		$this->assertCount(1, $instance->getServerList());
	}