public function flush(UnitTester $I)
{
$I->wantTo('Flush cache by using Memcache as cache backend');
$cache = new Memcache(new Data(['lifetime' => 20]), ['host' => TEST_MC_HOST, 'port' => TEST_MC_PORT, 'statsKey' => '_PHCM']);
$key1 = 'data-flush-1';
$key2 = 'data-flush-2';
$I->haveInMemcached($key1, 1);
$I->haveInMemcached($key2, 2);
$cache->save('data-flush-1', 1);
$cache->save('data-flush-2', 2);
$I->assertArrayHasKey('data-flush-1', $I->grabValueFromMemcached('_PHCM'));
$I->assertArrayHasKey('data-flush-2', $I->grabValueFromMemcached('_PHCM'));
$I->assertTrue($cache->flush());
$I->dontSeeInMemcached($key1);
$I->dontSeeInMemcached($key2);
$I->assertFalse($I->grabValueFromMemcached('_PHCM'));
$I->clearMemcache();
}