The Golden Rule of Assertions

What if I told you there was a single rule that can reliably tell apart a good test from a bad one? This is not a trick, not a sales pitch. It’s a rule I’ve been using for years to help me refine my tests, make them less flaky and more valuable countless times. In fact, it’s such an indispensable rule in practice that I hereby coin it The Golden Rule of Assertions: A test must fail if, and only if

[jay-es]

「テストが失敗するのは、システムの意図が達成されない場合のみでなければいけない」 。対応の一例として、実装の詳細はテストしない、外部要因（API など）に依存するコードの場合はモックを使用する、など