def test_external_refs_draft6(self):

        schema_1 = {
            '$id': 'http://example.com/schema_1.json',
            'properties': {
                'a': {'$ref': "schema_2.json#/definitions/a"},
            },
        }

        schema_2 = {
            '$id': 'http://example.com/schema_2.json',
            'definitions': {
                "a": {
                    "properties": {
                        "b": {'mergeStrategy': 'version'},
                    }
                },
            }
        }

        merger = jsonmerge.Merger(schema_1, validatorclass=Draft6Validator)

        # merge() would otherwise make a HTTP request
        merger.cache_schema(schema_2)

        base = None
        base = merger.merge(base, {"a": {"b": "c"}})
        base = merger.merge(base, {"a": {"b": "d"}})

        self.assertEqual(base, {"a": {"b": [{"value": "c"}, {"value": "d"}]}})