### Question:
CoAPTxRequestPacket extends XBeeAPIPacket { public void setDestAddress(Inet6Address destAddress) { if (destAddress == null) throw new NullPointerException(ERROR_DEST_ADDR_NULL); this.destAddress = destAddress; } CoAPTxRequestPacket(int frameID, int transmitOptions, HTTPMethodEnum method,
			Inet6Address destAddress, String uri, byte[] payload); static CoAPTxRequestPacket createPacket(byte[] payload); @Override boolean needsAPIFrameID(); @Override boolean isBroadcast(); void setTransmitOptions(int transmitOptions); int getTransmitOptions(); void setMethod(HTTPMethodEnum method); HTTPMethodEnum getMethod(); void setDestAddress(Inet6Address destAddress); Inet6Address getDestAddress(); void setURI(String uri); String getURI(); void setPayload(byte[] payload); byte[] getPayload(); @Override LinkedHashMap<String, String> getAPIPacketParameters();  }### Answer:
@Test public final void testSetDestAddressNull() { CoAPTxRequestPacket packet = new CoAPTxRequestPacket(frameID, options, method, destAddress, uriData, data); exception.expect(NullPointerException.class); exception.expectMessage(is(equalTo("Destination address cannot be null."))); packet.setDestAddress(null); }