public function writePoFile(string $file): void
    {
        $source = $this->dumpString();
        $testName = file_exists($file) ? $file : dirname($file);
        $status = is_writable($testName);
        if ($status === true) {
            $status = file_put_contents($file, $source);
        }
        if (false === $status) {
            throw new FileNotWritableException($file);
        }
    }