public function testSerializeObjectWithRelations()
 {
     $author = new Author();
     $author->setFirstName('John');
     $book = new Book();
     $book->setTitle('Foo4');
     $book->setISBN('1234');
     $book->setAuthor($author);
     $book->save();
     $b = clone $book;
     $sb = serialize($b);
     $book->clearAllReferences();
     $this->assertEquals($book, unserialize($sb));
 }