// Calculate the same using manual HMACT64 algorithm
        byte[] expectedResult = calculateHMACT64Manually(key, data);
        assertArrayEquals(expectedResult, result);
    }

    @Test
    void testHMACT64WithEmptyData() {
        // Test with empty data
        HMACT64 hmac = new HMACT64(TEST_KEY);
        hmac.engineUpdate(EMPTY_DATA, 0, EMPTY_DATA.length);
        byte[] result = hmac.engineDigest();

            hmac.engineUpdate(data, 0, data.length);
            byte[] result = hmac.engineDigest();

            assertArrayEquals(expected, result);
        }
    }

    @Test
    void testHMACT64WithEmptyData() throws NoSuchAlgorithmException {
        // Test with empty data
        byte[] key = "key".getBytes();
        byte[] data = EMPTY_DATA;

        MessageDigest md5 = MessageDigest.getInstance("MD5");