public function testReadPrimaryPreferred()
{
$qb = $this->collection->find()->readPrimaryPreferred(array(array('dc' => 'kyiv'), array('dc' => 'lviv')));
$qb->current();
$this->assertEquals(array('type' => \MongoClient::RP_PRIMARY_PREFERRED, 'tagsets' => array(array('dc' => 'kyiv'), array('dc' => 'lviv'))), $qb->getReadPreference());
}