void check(const QModelIndex &idx, QAbstractItemModel *model)
{
  const bool hasChildren = model->hasChildren(idx);
  const int rowCount = model->rowCount(idx);

  if (hasChildren) {
      Q_ASSERT(rowCount > 0);
      QModelIndex ni = model->index(0, 0, idx);
      Q_ASSERT(ni.isValid());
      check(ni, model);
  } else {
      Q_ASSERT(rowCount == 0);
  }
}

int main(int argc, char **argv)
{
  QApplication app(argc, argv);

  QFileSystemModel model;
  model.setRootPath(QDir::currentPath());

  check(QModelIndex(), &model);

  app.exec();
}