private function findSourceFiles(): void
  {
    $helper    = new SourceFinderHelper(dirname($this->configFilename));
    $filenames = $helper->findSources($this->sourcePattern);

    foreach ($filenames as $filename)
    {
      $routineName     = pathinfo($filename, PATHINFO_FILENAME);
      $this->sources[] = ['path_name'    => $filename,
                          'routine_name' => $routineName,
                          'method_name'  => $this->methodName($routineName)];
    }
  }