// Test constructor with a key shorter than BLOCK_LENGTH (64 bytes)
        HMACT64 hmac = new HMACT64(SHORT_TEST_KEY);
        assertNotNull(hmac);
    }

    @Test
    void testEngineUpdateByte() {
        // Test engineUpdate(byte b)
        HMACT64 hmac = new HMACT64(TEST_KEY);
        hmac.engineUpdate((byte) 0x01);
        // No exception means success
    }

    @Test

            assertNotNull(hmac);
            verify(mockMd5, times(1)).reset();
            verify(mockMd5, times(1)).update(any(byte[].class)); // Should update with ipad
        }
    }

    @Test
    void testEngineUpdateByte() throws NoSuchAlgorithmException {
        // Test engineUpdate(byte b)
        try (MockedStatic<Crypto> mockedCrypto = mockStatic(Crypto.class)) {
            mockedCrypto.when(Crypto::getMD5).thenReturn(mockMd5);