日付や時刻のテスト
https://t-wada.hatenablog.jp/entry/design-for-testability
例題
https://qiita.com/yasuabe2613/items/fbdd139f00161ff3186d
scalaの解答例
https://miwa719.hatenablog.com/entry/daily20210912
https://t-wada.hatenablog.jp/entry/design-for-testability
https://qiita.com/yasuabe2613/items/fbdd139f00161ff3186d