   #   The function to execute on each directory, receives a single argument the
   #   absolute path (defaults to onFile)
   traverseTreeSync: (rootPath, onFile, onDirectory=onFile) ->
-    return unless @isDirectorySync(rootPath)
+    return unless fsPlus.isDirectorySync(rootPath)
 
     traverse = (directoryPath, onFile, onDirectory) ->
       for file in fs.readdirSync(directoryPath)

  # Public: Create a directory at the specified path including any missing
  # parent directories synchronously.
  makeTreeSync: (directoryPath) ->
    mkdirp.sync(directoryPath) if directoryPath and not @existsSync(directoryPath)

  # Public: Recursively walk the given path and execute the given functions
  # synchronously.

  #   An array of extensions to filter the results by. If none are given, none
  #   are filtered (optional).
  listSync: (rootPath, extensions) ->
    return [] unless fsPlus.isDirectorySync(rootPath)
    paths = fs.readdirSync(rootPath)
    paths = fsPlus.filterExtensions(paths, extensions) if extensions
    paths = paths.map (childPath) -> path.join(rootPath, childPath)
    paths

