make the test simpler by using a new doc class

tests/queryset/queryset.py

@@ -2200,23 +2200,18 @@ class QuerySetTest(unittest.TestCase):
 
     def test_comment(self):
         """Make sure adding a comment to the query works."""
-        self.Person.drop_collection()
+        class User(Document):
+            age = IntField()
 
         with db_ops_tracker() as q:
-            adult = (self.Person.objects.filter(age__gte=18)
+            adult = (User.objects.filter(age__gte=18)
                 .comment('looking for an adult')
                 .first())
             ops = q.get_ops()
-            import pprint
-            pprint.pprint(ops)
             self.assertEqual(len(ops), 1)
             op = ops[0]
-            self.assertEqual(op['query']['$query'], {
-                '_cls': 'Person',
-                'age': {'$gte': 18}
-            })
-            self.assertEqual(op['query']['$comment'],
-                             'looking for an adult')
+            self.assertEqual(op['query']['$query'], {'age': {'$gte': 18}})
+            self.assertEqual(op['query']['$comment'], 'looking for an adult')
 
     def test_map_reduce(self):
         """Ensure map/reduce is both mapping and reducing.