public function testDefaultPersistentCollectionGenerator()
{
$c = new Configuration();
$c->setPersistentCollectionDir(__DIR__ . '/../../../../PersistentCollections');
$c->setPersistentCollectionNamespace('PersistentCollections');
$generator = $c->getPersistentCollectionGenerator();
$this->assertInstanceOf(PersistentCollectionGenerator::class, $generator);
$this->assertSame($generator, $c->getPersistentCollectionGenerator());
}