protected static function phpunit(): string
    {
        $vendor = static::vendorDir();

        $phpunit = $vendor . \DIRECTORY_SEPARATOR . 'phpunit' . \DIRECTORY_SEPARATOR . 'phpunit' . \DIRECTORY_SEPARATOR . 'phpunit';
        if (file_exists($phpunit)) {
            return $phpunit;
        }

        return 'phpunit';
    }