anchor.diff:  import 'dart:convert';
   import 'dart:io';
   import 'package:observatory/service_io.dart';
  +
  +bool _isWebSocketDisconnect(e) {
  +  if (e is! ServiceException) {
  +    return false;
  +  }
  +  return (e as ServiceException).message == 'WebSocket disconnected';
  +}
   
   // This invocation should set up the state being tested.
   const String _TESTEE_MODE_FLAG = "--testee-mode";
  
positive.code:       var testIndex = 0;
        var totalTests = tests.length - 1;
        var name = Platform.script.pathSegments.last;
        new WebSocketVM(new WebSocketVMTarget(addr)).load()
            .then((VM vm) => Future.forEach(tests, (test) {
              print('Running $name [$testIndex/$totalTests]');
              testIndex++;
              return test(vm);
            })).then((_) => process.requestExit());
      });
    }
  }
  
negative.code:       var testIndex = 0;
        var totalTests = tests.length - 1;
        var name = Platform.script.pathSegments.last;
        runZoned(() {
          new WebSocketVM(new WebSocketVMTarget(addr)).load()
              .then((VM vm) => vm.isolates.first.load())
              .then((Isolate isolate) => Future.forEach(tests, (test) {
                print('Running $name [$testIndex/$totalTests]');
                testIndex++;
                return test(isolate);
              })).then((_) => process.requestExit());
        }, onError: (e, st) {
          if (!_isWebSocketDisconnect(e)) {
            print('Unexpected exception in service tests: $e $st');
            throw e;
          }
        });
      });
    }
  }
  