added test cases for update pull queries

tests/queryset/transform.py

@@ -248,6 +248,30 @@ class TransformTest(unittest.TestCase):
         with self.assertRaises(InvalidQueryError):
             events.count()
     
+    def test_update_pull_for_list_fields(self):
+        """ 
+        Test added to check pull operation in update for 
+        EmbeddedDocumentListField which is inside a EmbeddedDocumentField
+        """
+        class Word(EmbeddedDocument):
+            word = StringField()
+            index = IntField()
+        
+        class SubDoc(EmbeddedDocument):
+            heading = ListField(StringField())
+            text = EmbeddedDocumentListField(Word)
+        
+        class MainDoc(Document):
+            title = StringField()
+            content = EmbeddedDocumentField(SubDoc)
+        
+        word = Word(word='abc', index=1)
+        update = transform.update(MainDoc, pull__content__text=word)
+        self.assertEqual(update, {'$pull': {'content.text': SON([('word', u'abc'), ('index', 1)])}})
+
+        update = transform.update(MainDoc, pull__content__heading='xyz')
+        self.assertEqual(update, {'$pull': {'content.heading': 'xyz'}})
+        
         
 if __name__ == '__main__':
     unittest.main()