assertNotNull(result);
    }

    @Test
    void testEngineGetDigestLength() {
        // 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);

        // Test engineGetDigestLength()
        try (MockedStatic<Crypto> mockedCrypto = mockStatic(Crypto.class)) {
            mockedCrypto.when(Crypto::getMD5).thenReturn(mockMd5);
            when(mockMd5.getDigestLength()).thenReturn(16); // MD5 digest length is 16
            HMACT64 hmac = new HMACT64(TEST_KEY);
            assertEquals(16, hmac.engineGetDigestLength());

        try {
            return md5.digest(buf, offset, len);
        } catch (final Exception ex) {
            throw new IllegalStateException();
        }
    }

    @Override
    protected int engineGetDigestLength() {
        return md5.getDigestLength();
    }

    @Override
    protected void engineReset() {
        md5.reset();
        md5.update(ipad);
    }

    @Override

        try {
            return this.md5.digest(buf, offset, len);
        } catch (final Exception ex) {
            throw new IllegalStateException();
        }
    }

    @Override
    protected int engineGetDigestLength() {
        return this.md5.getDigestLength();
    }

    @Override
    protected void engineReset() {
        this.md5.reset();
        this.md5.update(this.ipad);
    }

    @Override