anchor.diff:          var snapshot = result.snapshot;
           expect(snapshot.hasChildren, false);
           expect(snapshot.numChildren, 0);
  -        expect(snapshot.val(), null);
  +        expect(snapshot.val(), 43);
         });
       });
     });
  
positive.code: import 'package:firebase/firebase.dart';
  import 'package:scheduled_test/scheduled_test.dart';
  import 'package:unittest/html_config.dart';
  
negative.code:       });
      });
  
      test('simple value, existing value', () {
        var testRef = f.child('tx3');
        return testRef.set(42).then((_) {
          return testRef.transaction((curVal) {
            expect(curVal == null || curVal == 42, isTrue);
            return 43;
          });
        }).then((result) {
          expect(result.committed, isTrue);
  