}

    @Test
    @DisplayName("writeSecurityBuffer writes zero length buffer unchanged")
    void testWriteSecurityBufferZeroLength() {
        byte[] dest = new byte[10];
        byte[] before = dest.clone();
        NtlmMessage.writeSecurityBuffer(dest, 0, 4, null);
        assertArrayEquals(before, dest, "Zero length should leave dest unchanged");
    }

    }

    @Test
    void testWriteSecurityBuffer() {
        // Test writeSecurityBuffer
        byte[] dest = new byte[8]; // Enough for length, max_length, offset
        byte[] src = "Test".getBytes();

        // Test with non-null source array
        int nextOffset = NtlmMessage.writeSecurityBuffer(dest, 0, src);
        assertEquals(4, nextOffset, "Should return correct next offset.");

            System.arraycopy(NTLMSSP_SIGNATURE, 0, type1, 0, 8);
            writeULong(type1, 8, 1);
            writeULong(type1, 12, flags);
            if (hostInfo) {
                writeSecurityBuffer(type1, 16, 32, domain);
                writeSecurityBuffer(type1, 24, 32 + domain.length, workstation);
            }
            return type1;
        } catch (final IOException ex) {

            int offset = 64;
            writeSecurityBuffer(type3, 12, offset, lmResponse);
            offset += lmLength;
            writeSecurityBuffer(type3, 20, offset, ntResponse);
            offset += ntLength;
            writeSecurityBuffer(type3, 28, offset, domain);
            offset += domainLength;
            writeSecurityBuffer(type3, 36, offset, user);
            offset += userLength;

        pos += NTLMSSP_SIGNATURE.length;

        writeULong(type2, pos, NTLMSSP_TYPE2);
        pos += 4;

        // TargetNameFields
        final int targetNameOff = writeSecurityBuffer(type2, pos, targetBytes);
        pos += 8;

        writeULong(type2, pos, flags);
        pos += 4;

        // ServerChallenge
        final byte[] challengeBytes = getChallenge();

        pos += 4;

        final int lmOff = writeSecurityBuffer(type3, 12, lmResponseBytes);
        pos += 8;
        final int ntOff = writeSecurityBuffer(type3, 20, ntResponseBytes);
        pos += 8;
        final int domOff = writeSecurityBuffer(type3, 28, domainBytes);
        pos += 8;
        final int userOff = writeSecurityBuffer(type3, 36, userBytes);
        pos += 8;

            pos += 4;

            writeULong(type1, pos, flags);
            pos += 4;

            final int domOffOff = writeSecurityBuffer(type1, pos, domain);
            pos += 8;

            final int wsOffOff = writeSecurityBuffer(type1, pos, workstation);
            pos += 8;

            if ((flags & NTLMSSP_NEGOTIATE_VERSION) != 0) {

    static void writeUShort(final byte[] dest, final int offset, final int ushort) {
        dest[offset] = (byte) (ushort & 0xff);
        dest[offset + 1] = (byte) (ushort >> 8 & 0xff);
    }

    static void writeSecurityBuffer(final byte[] dest, final int offset, final int bodyOffset, final byte[] src) {
        final int length = src != null ? src.length : 0;
        if (length == 0) {
            return;
        }

            System.arraycopy(NTLMSSP_SIGNATURE, 0, type2, 0, 8);
            writeULong(type2, 8, 2);
            writeSecurityBuffer(type2, 12, data, target);
            writeULong(type2, 20, flags);
            System.arraycopy(challenge != null ? challenge : new byte[8], 0, type2, 24, 8);
            if (context != null) {

    static void writeUShort(final byte[] dest, final int offset, final int ushort) {
        dest[offset] = (byte) (ushort & 0xff);
        dest[offset + 1] = (byte) (ushort >> 8 & 0xff);
    }

    static int writeSecurityBuffer(final byte[] dest, final int offset, final byte[] src) {
        final int length = src != null ? src.length : 0;
        if (length == 0) {
            return offset + 4;
        }