anchor.diff:      await _server?.close();
     }
   
  +  void resetState() {
  +    _vm = MockVM(this);
  +    messages.clear();
  +  }
  +
     @override
     dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
  +
   }
   
   class MockVM implements VM {
  
positive.code:       // simulate package
        await _createPackage(fs, 'somepkg', 'somefile.txt');
  
        devFS = DevFS(vmService, 'test', tempDir);
        await devFS.create();
        vmService.expectMessages(<String>['create test']);
        expect(devFS.assetPathsToEvict, isEmpty);
  
negative.code:     });
  
      testUsingContext('correctly updates last compiled time when compilation does not fail', () async {
        // simulate package
        final File sourceFile = await _createPackage(fs, 'somepkg', 'main.dart');
  
  