anchor.diff:  
   Configuration _config;
   
  -/// [Configuration] used by the unittest library. Note that if a
  -/// configuration has not been set, calling this getter will create
  -/// a default configuration.
  +/// [Configuration] used by the unittest library.
  +///
  +/// Note that if a configuration has not been set, calling this getter will
  +/// create a default configuration.
   Configuration get unittestConfiguration {
     if (_config == null) {
       _config = new Configuration();
  
positive.code:     {String id, String reason}) =>
    new _SpreadArgsHelper(callback, 0, -1, id, reason, isDone: isDone).func;
  
  /// Creates a new named group of tests. Calls to group() or test() within the
  /// body of the function passed to this will inherit this group's description.
  void group(String description, void body()) {
    ensureInitialized();
    _requireNotRunning();
  
negative.code: bool formatStacks = true;
  
  /// A flag that controls whether we try to filter out irrelevant frames from
  /// the stack trace.
  ///
  /// Requires [formatStacks] to be set.
  bool filterStacks = true;
  
  void _requireNotRunning() {
  