テスト駆動開発の第Ⅰ部 他国通過をTypeScriptで写経 Setup yarn Test run test yarn test watch yarn watch References https://jestjs.io https://ky-yk-d.hatenablog.com/entry/2018/11/11/071020 https://typescript-jp.gitbook.io/deep-dive/recap/number https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map https://github.com/cm-pliser-tdd-by-example/tdd-by-example-js