anchor.diff:        expect(e.message.startsWith('I always throw!\n'), isTrue);
       }
   
  -    try {
  -      await isolate.invokeRpcNoUpgrade('ext..null', {});
  -    } on ServerRpcException catch (e, st) {
  -      expect(e.code, equals(ServiceExtensionResponse.extensionError));
  -      expect(e.message, equals('Extension handler must return a Future'));
  -    }
  -
  -    try {
  -      await isolate.invokeRpcNoUpgrade('ext..nullFuture', {});
  -    } on ServerRpcException catch (e, st) {
  -      expect(e.code, equals(ServiceExtensionResponse.extensionError));
  -      expect(
  -          e.message,
  -          equals('Extension handler must complete to a '
  -              'ServiceExtensionResponse'));
  -    }
  -
       result =
           await isolate.invokeRpcNoUpgrade('ext..success', {'apple': 'banana'});
       expect(result['type'], equals('_extensionType'));
  
positive.code:     expect(isolate.extensionRPCs, contains('ext..delay'));
      expect(isolate.extensionRPCs, isNot(contains('ext..error')));
      expect(isolate.extensionRPCs, isNot(contains('ext..exception')));
      expect(isolate.extensionRPCs, isNot(contains('ext..null')));
      expect(isolate.extensionRPCs, isNot(contains('ext..nullFuture')));
      expect(isolate.extensionRPCs, isNot(contains('ext..success')));
    },
    resumeIsolateAndAwaitEvent(Isolate.kExtensionStream, (ServiceEvent event) {
  
negative.code:   debugger();
    registerExtension('ext..error', Handler);
    registerExtension('ext..exception', Handler);
    registerExtension('ext..success', Handler);
    bool exceptionThrown = false;
    try {
  