anchor.diff:  library dartivity.test;
   
   import 'dart:async';
  +import 'dart:io';
   
   import 'package:dartivity/dartivity.dart';
   
   Future main() async {
  +  final int badExitCode = -1;
  +
     // Instantiate a Dartivity client and initialise for
     // messaging only
     Dartivity dartivity = new Dartivity(Mode.messagingOnly);
  
positive.code:     print("Message not sent not ready - OK");
    } else {
      print("Oops message sent when not ready- ERROR");
    }
  
    // Initialise
  
negative.code:     print("Null message not sent - OK");
    } else {
      print("Oops null message sent - ERROR");
      exit(badExitCode);
    }
  
    // Send a couple of whoHas messages
  