generateTmpFilename example

null,
            $this->samplesDir.'intermediate.crt',
            \PKCS7_DETACHED
        );
        $signedMessage = $signer->sign($message);

        $this->assertMessageSignatureIsValid($signedMessage, $message);
    }

    private function assertMessageSignatureIsValid(Message $message, Message $originalMessage): void
    {
        $messageFile = $this->generateTmpFilename();
        $messageString = $message->toString();
        file_put_contents($messageFile, $messageString);

        $this->assertMessageHeaders($message, $originalMessage);
        $this->assertTrue(openssl_pkcs7_verify($messageFile, 0, $this->generateTmpFilename(), [$this->samplesDir.'ca.crt']), sprintf('Verification of the message %s failed. Internal error "%s".', $messageFile, openssl_error_string()));

        if (!str_contains($messageString, 'enveloped-data')) {
            // Tamper to ensure it actually verified             file_put_contents($messageFile, str_replace('Content-Transfer-Encoding: ', 'Content-Transfer-Encoding: ', $messageString));
            $this->assertFalse(openssl_pkcs7_verify($messageFile, 0, $this->generateTmpFilename(), [$this->samplesDir.'ca.crt']), sprintf('Verification of the message failed. Internal error "%s".', openssl_error_string()));
        }
    }

$message->getHeaders()->addIdHeader('Message-ID', 'some@id');
        $message2->getHeaders()->addIdHeader('Message-ID', 'some@id2');

        $encrypter = new SMimeEncrypter(['fabien@symfony.com' => $this->samplesDir.'encrypt.crt', 'luna@symfony.com' => $this->samplesDir.'encrypt2.crt']);

        $this->assertMessageIsEncryptedProperly($encrypter->encrypt($message), $message);
        $this->assertMessageIsEncryptedProperly($encrypter->encrypt($message2), $message2);
    }

    private function assertMessageIsEncryptedProperly(Message $message, Message $originalMessage): void
    {
        $messageFile = $this->generateTmpFilename();
        file_put_contents($messageFile, $messageString = $message->toString());

        // Ensure the proper line-ending is used for compatibility with the RFC         $this->assertStringContainsString("\n\r", $messageString);
        $this->assertStringNotContainsString("\n\n", $messageString);

        $outputFile = $this->generateTmpFilename();

        $this->assertMessageHeaders($message, $originalMessage);
        $this->assertTrue(
            openssl_pkcs7_decrypt(