public function testSerialize()
 {
     $book = new Book($this->conn, ['id' => 3, 'name' => 'foo']);
     $details = new BookDetails($this->conn, ['books_id' => 3]);
     $book->setRelation('details', $details);
     $stored = serialize($book);
     $fetched = unserialize($stored);
     $this->assertSame($book->getValues(), $fetched->getValues());
     $this->assertSame($details->getValues(), $fetched->details->getValues());
 }