PhpCsFixer\Test\IntegrationCaseFactory::determineExpectedCode PHP Method

    protected function determineExpectedCode($code, SplFileInfo $file)
    {
        $code = $this->determineCode($code, $file, '-out.php');
        if (null === $code) {
            throw new \InvalidArgumentException('Missing expected code.');
        }
        return $code;
    }