### Question:
ConnAckDecoder extends MqttDecoder { public MessageDecoderResult decodable(IoSession session, IoBuffer in) { return Utils.checkDecodable(AbstractMessage.CONNACK, in); }  MessageDecoderResult decodable(IoSession session, IoBuffer in); MessageDecoderResult decode(IoSession session, IoBuffer in, ProtocolDecoderOutput out);  }### Answer:
@Test public void testDecodable_NOT_OK() { m_buff.put((byte)(AbstractMessage.CONNECT << 4)) .put((byte)0) .flip(); assertEquals(MessageDecoder.NOT_OK , m_msgdec.decodable(null, m_buff)); }
@Test public void testDecodable_OK() { m_buff.put((byte)(AbstractMessage.CONNACK << 4)) .put((byte)0) .flip(); assertEquals(MessageDecoder.OK , m_msgdec.decodable(null, m_buff)); }