anchor.diff:  import 'dart:math';
   
   void main() {
  -  var dummySerialPort;
  -  var random = new Random();
  +  File dummySerialPort;
  +  Random random = new Random();
     group('Serial port', () {
       setUp(() {
  -      //dummySerialPort = new File("dummySerialPort-${random.nextInt(999)}.tmp").createSync();
         dummySerialPort = new File("dummySerialPort.tmp");
         return dummySerialPort.create();
       });
  
positive.code:                    .then((success) =>  expect(success, isTrue));
      });
  
      test('Defaut baudrate 9600', () {
        var serial =  new SerialPort(dummySerialPort.path);
        expect(serial.baudrate, 9600);
      });
  
      test('Just write', () {
        var serial =  new SerialPort(dummySerialPort.path);
        serial.open().then((_) => serial.write("Hello"))
  
negative.code:                       expect(success, isTrue);
                        serial.close();
                     });
      });
  
      test('Defaut baudrate 9600', () {
        var serial =  new SerialPort(dummySerialPort.path);
        expect(serial.baudrate, 9600);
      });
  
      test('Fail with unkwnon portname', (){
  