Regression Test Plan Skill

Regression testing protects what already works — but re-running everything every time is slow and wasteful, and testing too little ships breakage. The answer is risk-based: re-test what changed, what it touches, and what hurts most if it breaks. This skill builds that prioritised plan and a run strategy, so coverage tracks risk and the suite doesn't balloon.

Working from a brief

Given "we're shipping a checkout change, what should we regression-test?", produce the plan anyway — infer the impacted areas and a sensible prioritisation, labelling assumptions. Tie scope to change-impact and risk. Never hand back a question instead of a plan.

Required Inputs

Ask for these only if they aren't already provided (else infer and label):

• The change — what's being released/modified, and what it touches (and integrates with).
• Critical paths — the flows that must never break (revenue, auth, data integrity).
• Existing coverage — current regression cases/automation, if any, and how long a full run takes.
• Constraints — time/resources per release, and manual vs. automated capacity.

Output Format

Regression Plan: release/change]

1. Impact analysis — what changed, the areas directly and indirectly affected, and the high-risk zones (shared components, recent bugs, complex logic).

2. Prioritised scope — what to re-test, in tiers:

| Tier | When to run | Scope | Why | |---|---|---|---| | Smoke / sanity | every build | critical paths only (login, checkout, save) | fast fail | | Targeted | this change | the changed area + its direct dependencies | change-impact | | Full regression | major release / risky change | broad core coverage | safety net |

3. What to skip (and the risk) — explicitly de-scope low-risk, unchanged areas, and name the residual risk.

4. Automation candidates — which cases are stable, high-value, and repetitive enough to automate first (and which to keep manual).

5. Run strategy — when each tier runs (per-commit / per-release), order (critical first), and the entry/exit criteria for sign-off.

Quality Checks

• ] Scope is driven by change-impact and risk, not "run everything" or "run the same list every time"
• ] Critical paths are always covered (a fast smoke tier)
• ] De-scoped areas are explicit, with the residual risk named
• ] Automation candidates are prioritised by stability and value
• ] A run strategy ties each tier to when it runs and the sign-off criteria
• ] The suite stays proportionate to the time/risk — not bloated

Anti-Patterns

• ] Do not "re-run everything" by default — it's slow and trains teams to skip it
• ] Do not test only the changed file — cover its dependencies and shared components
• ] Do not silently drop coverage — when you de-scope, state the risk
• ] Do not automate flaky or rarely-run cases first — start with stable, high-value ones
• ] Do not let the suite grow unbounded — prune and tier it as the product changes

Based On

Risk-based regression practice — change-impact analysis, tiered smoke/targeted/full suites, automation prioritisation, and release-fit run strategy.