anchor.diff:  }
   
   /// Responds with the updates test to the [request].
  -_updateTest(request) {
  +_updatesTest(request) {
     var queries = _parseInt(request.uri.queryParameters['queries']).clamp(1, 500);
  -  var worlds = new List<World>(queries);
  -  Future.wait(new List.generate(queries, (index) {
  -    return _connectionPool.connect().then((connection) {
  -      return connection.query(
  -              'SELECT id, randomNumber FROM world WHERE id = @id;',
  -              { 'id': _RANDOM.nextInt(_WORLD_TABLE_SIZE) + 1 })
  -          .toList()
  -          .then((rows) {
  -            //
  -            // The benchmark's constraints tell us there is exactly one row.
  -            //
  -            var row = rows[0];
  -            worlds[index] = new World(row[0], row[1]);
  -          })
  -          .whenComplete(() { connection.close(); });
  -    });
  -  }, growable: false)).then((_) {
  -    Future.wait(new List.generate(queries, (int index) {
  -      var world = worlds[index];
  -      world.randomNumber = _RANDOM.nextInt(_WORLD_TABLE_SIZE) + 1;
  -      return _connectionPool.connect().then((connection) {
  -        return connection.execute(
  +  Future.wait(new List.generate(queries, (_) {
  +    return _queryRandom()
  +        .then((world) {
  +          world.randomNumber = _RANDOM.nextInt(_WORLD_TABLE_SIZE) + 1;
  +          return _connectionPool.connect().then((connection) {
  +            return connection.execute(
                   'UPDATE world SET randomNumber = @randomNumber WHERE id = @id;',
                   { 'randomNumber': world.randomNumber, 'id': world.id })
  -            .whenComplete(() { connection.close(); });
  -      });
  -    }, growable: false)).then((_) { _sendJson(request, worlds); });
  -  });
  +                .whenComplete(() { connection.close(); });
  +          }).then((_) => world);
  +        });
  +  }, growable: false))
  +      .then((worlds) => _sendJson(request, worlds));
   }
   
   /// Responds with the plaintext test to the [request].
  
positive.code:     })
    ]).then((_) {
      HttpServer.bind(address, port).then((server) {
        server.listen((request) {
          switch (request.uri.path) {
            case '/':
              _jsonTest(request);
              break;
            case '/db':
              _dbTest(request);
              break;
            case '/fortunes':
              _fortunesTest(request);
              break;
            case '/update':
              _updateTest(request);
              break;
            case '/plaintext':
              _plaintextTest(request);
  
negative.code: import 'dart:async' show Future;
  import 'dart:io';
  import 'dart:utf';
  import 'dart:json' as json;
  import 'dart:math' show Random;
  import 'package:args/args.dart' show ArgParser;
  