#vulnerable code 
                                @Test
    public void testDecode() throws IOException {
        Packet packet = decoder.decodePacket("4:::\"2\"", null);
//        Assert.assertEquals(PacketType.JSON, packet.getType());
        Assert.assertEquals("2", packet.getData());
    } 
                            #location 5 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void testDecode() throws IOException {
        Packet packet = decoder.decodePackets(Unpooled.copiedBuffer("4:::\"2\"", CharsetUtil.UTF_8), null);
//        Assert.assertEquals(PacketType.JSON, packet.getType());
        Assert.assertEquals("2", packet.getData());
    }