Cache\Adapter\Common\CacheItem::expiresAfter PHP Method

    public function expiresAfter($time)
    {
        if ($time === null) {
            $this->expirationDate = null;
        }
        if ($time instanceof \DateInterval) {
            $this->expirationDate = new \DateTime();
            $this->expirationDate->add($time);
        }
        if (is_int($time)) {
            $this->expirationDate = \DateTime::createFromFormat('U', time() + $time);
        }
        return $this;
    }

 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());
 }