code: public void sendPayload(String payload) {
  		MessageEnvelope envelope = new MessageEnvelope();
  		Postback postback = new Postback();
  
  		postback.setPayload(payload);
  		envelope.setPostback(postback);
  		envelope.setSender(new User(facebookMockId));
  
  		System.out.println("Sending payload: [" + payload + "] as user : ["
  				+ facebookMockId + "].");
  		forward(envelope);
  		System.out.println("Sent!");
  	}
docs: Sends a payload to all the registered bots. Used to simulate a user
  interacting with buttons.
  
  @param payload
  the payload to send.