anchor.diff:      lister.onDir = (String dirPath) {
         final name = new Path(dirPath).filename;
         assert(!map.containsKey(name));
  -      map[name] = {};
  +      map[name] = _dirPlaceHolder;
       };
   
       lister.onDone = (bool completed) {
  
positive.code: part of bot_io;
  
  class IoHelpers {
    static Future<bool> verifyContents(Directory dir, Map<String, dynamic> content) {
      assert(dir != null);
      assert(content != null);
  
negative.code:       final subDirPath = new Path(parentDir.path).append(name);
        final subDir = new Directory.fromPath(subDirPath);
  
        assert(foundContent == _dirPlaceHolder);
  
        return _verifyContents(subDir, expectedContent);
      } else {
  