anchor.diff:        ],
     ]..shuffle(math.Random(0));
   
  -  if (!await _runShardRunnerIndexOfTotalSubshard(tests)) {
  -    // TODO(jmagman): Remove fallback once LUCI configs are migrated to d+_d+ subshard format.
  -    await _selectIndexedSubshard(tests, kBuildTestShardCount);
  -  }
  +  await _runShardRunnerIndexOfTotalSubshard(tests);
   }
   
   Future<void> _runExampleProjectBuildTests(FileSystemEntity exampleDirectory) async {
  
positive.code:   return tests.sublist(start, end);
  }
  
  Future<bool> _runShardRunnerIndexOfTotalSubshard(List<ShardRunner> tests) async {
    final List<ShardRunner> sublist = _selectIndexOfTotalSubshard<ShardRunner>(tests);
    // TODO(jmagman): Remove the boolean return to indicate fallback to unsharded variant once LUCI configs are migrated to d+_d+ subshard format.
    if (sublist == null) {
      return false;
    }
    for (final ShardRunner test in sublist) {
      await test();
    }
    return true;
  }
  
  /// If the CIRRUS_TASK_NAME environment variable exists, we use that to determine
  /// the shard and sub-shard (parsing it in the form shard-subshard-platform, ignoring
  /// the platform).
  ///
  /// However, for local testing you can just set the SHARD and SUBSHARD
  /// environment variables. For example, to run all the framework tests you can
  /// just set SHARD=framework_tests. To run specifically the third subshard of
  /// the Web tests you can set SHARD=web_tests SUBSHARD=2 (it's zero-based).
  Future<void> selectShard(Map<String, ShardRunner> shards) => _runFromList(shards, kShardKey, 'shard', 0);
  Future<void> selectSubshard(Map<String, ShardRunner> subshards) => _runFromList(subshards, kSubshardKey, 'subshard', 1);
  
negative.code:   return null;
  }
  
  /// Parse (one-)index/total-named subshards from environment variable SUBSHARD
  /// and equally distribute [tests] between them.
  /// Subshard format is "{index}_{total number of shards}".
  