regression-designlisted

# Regression Design Turn a behavior or bug into durable regression coverage guidance. This skill designs tests and evidence; it does not implement product fixes unless a test card explicitly authorizes Test to do so. ## Source Skills Used - `mattpocock/skills/engineering/tdd`: public interfaces, behavior over implementation, vertical red-green cycles, no horizontal test dumps, and no refactor while red. - `diagnose`: correct regression seam comes after a real feedback loop and reproduction. - Industry basis: test pyramid and behavior-focused testing. ## Wakeflow Role Use this skill when: - a bug has been reproduced and needs a regression plan; - a requirement needs behavior-first coverage before implementation; - a target result claims coverage and Test must judge whether the seam is right; - a controller wants to know what evidence would prevent recurrence. ## Core Principle Test observable behavior through a public seam. A good regression survives internal refactors. A bad regression tests private methods, mocks internal collaborators unnecessarily, or verifies implementation shape instead of user or system behavior. ## Workflow 1. Name the behavior. - What capability must remain true? - Which actor or integration observes it? 2. Choose the public seam. - API endpoint, CLI command, UI flow, public function, daemon job, integration boundary, or documented output. - Prefer the highest seam that proves the behavior. 3. Check the bug pattern.