class Base { ping() { return 1; } }

class Repo {
  load(key) { return key; }
  save(row) { return row; }
}

class Service extends Base {
  constructor(repo) { super(); this.repo = repo; }
  run(key) {
    const row = this.repo.load(key);
    return this.repo.save(row);
  }
}
