}

  static void SetTmpDir(const std::string& tmp_dir) {
    tmp_dir_ = tmp_dir.empty() ? ::testing::TempDir() : tmp_dir;
  }

 protected:
  Env* env_;

 private:
  std::string root_dir_;
  static int rng_val_;
  static std::string cloud_path_;
  static std::string tmp_dir_;
};

int ModularFileSystemTest::rng_val_;
std::string ModularFileSystemTest::cloud_path_;