def create_config_effect(self, cfg):
        """
        Returns a config "original" from a location with no config file
        and then the impact of applying the supplied cfg dictionary as
        a config file at a location in the returned "current".
        """

        # store original cwd
        original_cwd = os.getcwd()

        # create mock launch location
        launch_dir = self.mock_cfg_location()

        # switch cwd to the mock launch location, get and store settings
        os.chdir(launch_dir)
        # use override to ensure that the config is zero'd out with respect
        # to any existing settings
        with override_env_config('_', '_'):
            original = self.get_settings()

        # inject new config into a file in the mock launch location
        self.inject_mock_cfg(launch_dir, cfg)

        try:
            # override something but don't change the value, this is to refresh
            # the config and make sure the injected config file is read
            with override_env_config('_', '_'):
                current = self.get_settings()
        finally:
            # switch back to original dir with no new config
            os.chdir(original_cwd)
        return original, current

        Returns a config "original" from a location with no config file
        and then the impact of applying the supplied cfg dictionary as
        a config file at a location in the returned "current".
        
numba/tests/test_config.py