public function flush(UnitTester $I)
{
$I->wantTo('Flush all cache by using APC(u) as cache backend');
$cache = new Apc(new Data(['lifetime' => 20]));
$key1 = '_PHCA' . 'app-data' . 'data-flush-1';
$key2 = '_PHCA' . 'app-data' . 'data-flush-2';
$key3 = '_PHCA' . 'data-flush-3';
$I->haveInApc([$key1 => 1, $key2 => 2, $key3 => 3], null);
$I->assertTrue($cache->flush());
$I->dontSeeInApc($key1);
$I->dontSeeInApc($key2);
$I->dontSeeInApc($key3);
}