    def test_heterogeneous_properties_additionalProperties(self):
        """
        Not valid deserialized JSON, but this should not blow up.
        """
        schema = {"properties": {"foo": {}}, "additionalProperties": False}
        message = self.message_for(
            instance={"foo": {}, "a": "baz", 37: 12},
            schema=schema,
        )
        self.assertEqual(
            message,
            "Additional properties are not allowed (37, 'a' were unexpected)",
        )
Not valid deserialized JSON, but this should not blow up.
jsonschema/tests/test_validators.py