anchor.diff:        test('replace Uuid', () async {
           var collectionName = getRandomCollectionName();
           var collection = db.collection(collectionName);
  -        var uuid = UuidValue.v4();
  +        var uuid = Uuid().v4obj();
           await collection.insertOne({'uuid': uuid, 'null': null});
   
  -        var uuidNew = UuidValue.v4();
  +        var uuidNew = Uuid().v4obj();
           await collection.replaceOne(
               where.eq('notNull', 0), {'uuid': uuidNew, 'notNull': 0},
               upsert: true);
  
positive.code:     await db.open();
    }
  
    Future insertManyDocuments(
        DbCollection collection, int numberOfRecords) async {
      await collection.remove(<String, dynamic>{});
      var toInsert = <Map<String, dynamic>>[];
      for (var n = 0; n < numberOfRecords; n++) {
        toInsert.add({'a': Rational.fromInt(n)});
      }
  
      await collection.insertAll(toInsert);
    }
  
    Future cleanupDatabase() async {
      await db.close();
    }
  
negative.code:       test('delete Uuid', () async {
          var collectionName = getRandomCollectionName();
          var collection = db.collection(collectionName);
          var uuid = Uuid().v4obj();
          await collection.insertOne({'uuid': uuid, 'null': null});
  
          await collection.deleteOne(where.eq('uuid', uuid));
  