public function testSortUserDefinedInArrayCollection()
 {
     $collection = new ArrayCollection(array(5, 5, 4, 3, 2, 1, 0));
     $this->assertEquals(5, $collection->first());
     $collection->sort(function ($a, $b) {
         if ($a === $b) {
             return 0;
         }
         return $a < $b ? -1 : 1;
     });
     $this->assertEquals(5, $collection->last());
 }