Cache\Adapter\Common\CacheItem::getExpirationDate PHP Метод

    public function getExpirationDate()
    {
        return $this->expirationDate;
    }

 public function testExpiresAfter()
 {
     $item = new CacheItem('test_key');
     $this->assertNull($item->getExpirationDate());
     $item->expiresAfter(null);
     $this->assertNull($this->getExpectedException());
     $item->expiresAfter(new \DateInterval('PT1S'));
     $this->assertEquals(new \DateTime('+1 second'), $item->getExpirationDate());
     $item->expiresAfter(1);
     $this->assertEquals(new \DateTime('+1 second'), $item->getExpirationDate());
 }