'Test that the compound index doesn\'t get another _cls when it is specified'

def test_compound_index_underscore_cls_not_overwritten(self):

    class TestDoc(Document, ):
        shard_1 = StringField()
        txt_1 = StringField()
        meta = {'collection': 'test', 'allow_inheritance': True, 'sparse': True, 'shard_key': 'shard_1', 'indexes': [('shard_1', '_cls', 'txt_1')]}
    TestDoc.drop_collection()
    TestDoc.ensure_indexes()
    index_info = TestDoc._get_collection().index_information()
    self.assertTrue(('shard_1_1__cls_1_txt_1_1' in index_info))
