Add tests to ensure a panic occurs instead of segv

        assert!(priv_key.windows(11).any(|s| s == b"PRIVATE KEY"));

        assert!(pub_key.windows(10).any(|s| s == b"PUBLIC KEY"));

    }

    #[test]

    #[should_panic(expected = "Could not get RSA key for encryption")]

    fn test_nokey_encrypt() {

        let mut pkey = super::PKey::new();

        pkey.load_pub(&[]);

        pkey.encrypt(&[]);

    }

    #[test]

    #[should_panic(expected = "Could not get RSA key for decryption")]

    fn test_nokey_decrypt() {

        let mut pkey = super::PKey::new();

        pkey.load_priv(&[]);

        pkey.decrypt(&[]);

    }

    #[test]

    #[should_panic(expected = "Could not get RSA key for signing")]

    fn test_nokey_sign() {

        let mut pkey = super::PKey::new();

        pkey.load_priv(&[]);

        pkey.sign(&[]);

    }

    #[test]

    #[should_panic(expected = "Could not get RSA key for verification")]

    fn test_nokey_verify() {

        let mut pkey = super::PKey::new();

        pkey.load_pub(&[]);

        pkey.verify(&[], &[]);

    }

}