public static function assumeFreeDiskSpace($directory, $available = null, $message = ''): void
    {
        if ($available === null) {
            assumeThat(disk_free_space($directory), is(not(false)), $message);
        } else {
            assumeThat(disk_free_space($directory), is(greaterThanOrEqualTo($available)), $message);
        }
    }