def METHOD_NAME(self):
    Config.CONFIG = None  # Force config file reload
    with mock.patch.dict(
        "os.environ",
        {
            "APPDATA": os.path.dirname(__file__),
            "XDG_CONFIG_HOME": os.path.dirname(__file__),
        },
    ):
        config = Config("INTERPOLATION", config_interpolation="extended")
        assert config.custom["basic_interpolation"] == "%(reddit_url)s"
        assert config.custom["extended_interpolation"] == config.reddit_url