// Test engineGetDigestLength()
        HMACT64 hmac = new HMACT64(TEST_KEY);
        // MD5 digest length is 16 bytes
        assertEquals(16, hmac.engineGetDigestLength());
    }

    @Test
    void testEngineDigest() {
        // Test engineDigest()
        HMACT64 hmac = new HMACT64(TEST_KEY);
        hmac.engineUpdate(TEST_DATA, 0, TEST_DATA.length);
        byte[] result = hmac.engineDigest();

            HMACT64 hmac = new HMACT64(TEST_KEY);
            assertEquals(16, hmac.engineGetDigestLength());
            verify(mockMd5, times(1)).getDigestLength();
        }
    }

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