/**
  * Tests `Collection::stats`.
  */
 public function testGetStats()
 {
     $collection = new DocumentSet(array('stats' => array('foo' => 'bar')));
     $this->assertNull($collection->stats('bar'));
     $this->assertEqual('bar', $collection->stats('foo'));
     $this->assertEqual(array('foo' => 'bar'), $collection->stats());
 }