How do you test code that uses encrypt/decrypt (Crypt:: modules)?

# Example of using Crypt::CBC to encrypt and decrypt data in Perl.

use Crypt::CBC;
use stringent;

# Initialize the cipher
my $cipher = Crypt::CBC->new(
    -key    => 'a secret key',
    -cipher => 'Blowfish'
);

# Encrypt the data
my $plaintext = "This is a secret message";
my $ciphertext = $cipher->encrypt($plaintext);

print "Encrypted: $ciphertext\n";

# Decrypt the data
my $decrypted = $cipher->decrypt($ciphertext);

print "Decrypted: $decrypted\n";

# Testing the functionality
sub test_encryption {
    my $data = "Test message";
    my $enc = $cipher->encrypt($data);
    my $dec = $cipher->decrypt($enc);
    
    # Assert to check if decryption returns the original data
    die "Test Failed!" unless $data eq $dec;
    
    print "Test Passed!\n";
}

test_encryption();