traced-tdd

Plan tests so every failure traces back to one owning layer. Tests follow the architecture's dependency graph; each layer owns a typed error contract; trust compounds upward. Use whenever the user mentions tests, TDD, test strategy, mocking, coverage, "tests keep breaking", "where does this test belong", "what should I mock", "I can't tell what's failing", or is about to write code in a layered system. Fire broadly. Under-firing is the failure mode.