public function testFindAndModifyWithFields()
{
$id = '54203e08d51d4a1f868b456e';
$collection = $this->getCollection();
$document = ['_id' => new \MongoId($id), 'foo' => 'bar', 'bar' => 'foo'];
$collection->insert($document);
$document = $collection->findAndModify(['_id' => new \MongoId($id)], ['$set' => ['foo' => 'foo']], ['foo' => true]);
$this->assertArrayNotHasKey('bar', $document);
$this->assertArrayHasKey('foo', $document);
}