public function testPrePersist()
{
$dateCreated = new \DateTime();
$dateCreated = $dateCreated->format('yy');
$this->assertNull($this->unit->getCreatedAt());
$this->assertNull($this->unit->getUpdatedAt());
$this->unit->prePersist();
$this->assertEquals($dateCreated, $this->unit->getCreatedAt()->format('yy'));
$this->assertEquals($dateCreated, $this->unit->getUpdatedAt()->format('yy'));
}