anchor.diff:            'value': 'dark', // Intentionally invalid value.
           }
         );
  -      expect(bogusResponse.json['value'], 'Brightness.light');
  +      expect(bogusResponse.json?['value'], 'Brightness.light');
       });
   
       testWithoutContext('ext.flutter.debugPaint can toggle debug painting', () async {
  
positive.code:           'value': 'Brightness.dark',
          }
        );
        expect(updateResponse.json['value'], 'Brightness.dark');
  
        // Change the brightness back to light
        final Response verifyResponse = await vmService.callServiceExtension(
  
negative.code:         'ext.flutter.brightnessOverride',
          isolateId: isolate.id,
        );
        expect(response.json?['value'], 'Brightness.light');
  
        final Response updateResponse = await vmService.callServiceExtension(
          'ext.flutter.brightnessOverride',
  