assertEquals("Missing key", e.getMessage());
    }

    /**
     * Test calculateMac with an invalid algorithm type.
     */
    @Test
    void testCalculateMacInvalidAlgorithm() {
        Map<Integer, KerberosKey> keys = new HashMap<>();
        KerberosKey hmacKey = new KerberosKey(TEST_PRINCIPAL, new byte[16], PacSignature.ETYPE_ARCFOUR_HMAC, 0);