Analyzing Regression Scope

Use this skill when the real question is not "how do we test everything?" but "what must we retest now, and why?" It is built for risk-aware retest planning after code changes, configuration shifts, dependency updates, or release packaging.

When to Use

• analyze regression scope after a bug fix or feature change
• decide what must be retested for a hotfix
• prepare a release confidence suite from a diff or PR
• explain QA impact of shared component or config changes
• separate must-retest areas from nice-to-have regression coverage

Operating Principles

• Change surface first - understand what changed before proposing retest coverage.
• Risk spreads through dependencies - shared modules, auth, data mapping, and configuration often widen impact.
• Direct is not the whole story - the changed file is only the start; adjacent behaviors matter too.
• Small believable packs beat fake completeness - a focused confidence suite is better than a giant list nobody will execute.
• Unknown impact stays visible - if propagation is unclear, log it as an open question instead of bluffing.

Workflow

Phase 0: Frame the input

Use the best available source:

• changed files
• a diff or PR summary
• release notes
• a hotfix description
• a list of touched components or endpoints

Capture any known critical journeys, environments, or roles that matter.

Phase 1: Map the change surface

Break the change into four layers:

1. Directly changed behavior - the feature, endpoint, or component that was edited
2. Adjacent behavior - nearby flows that call, render, or depend on the changed surface
3. Shared risk - utilities, configuration, auth, layout, data mapping, or common services reused elsewhere
4. State and data risk - migrations, caching, permissions, synchronization, or environment-specific behavior

Phase 2: Classify retest risk

Use a practical three-level scale:

Risk	Use when
High	Direct change on a critical path, shared core module, data integrity flow, auth, checkout, notifications, or high-traffic workflow
Medium	Indirect dependency, shared helper, UI shell, validation logic, or meaningful edge-case exposure
Low	Isolated change with narrow blast radius and no obvious shared-path impact

Phase 3: Build the regression pack

Organize the result into four buckets:

• Must retest - confidence blockers; skipping these would be reckless
• Should retest - meaningful adjacent coverage if time allows
• Can sample - smoke-level checks instead of full retest
• Can defer with caution - lower-impact items worth tracking, not necessarily executing now

For every important area, include:

• why it is affected
• what to retest
• what data or environment setup is needed
• whether the coverage should stay manual or move into automation later

Phase 4: Produce the report

Use ./resources/regression-scope-template.md when possible.

A strong report includes:

• a short change summary
• a risk-ranked regression table
• a minimal confidence suite
• explicit open questions and blind spots

Common Failure Modes

• equating changed files with full regression scope
• producing a huge retest list with no priority
• ignoring shared components, config, or auth ripple effects
• forgetting data setup or role-specific behavior
• treating uncertainty as low risk without explanation

Resource Map

• ./resources/regression-scope-template.md - structure for regression reports and confidence suites

Related Skills

• designing-functional-tests - when the regression result should expand into manual scenarios or test cases
• verifying-acceptance-criteria - when the question becomes whether the feature now meets its stated contract
• requirements-test-coverage-mapper - when broader traceability matters more than tactical retest scope
• code-review-advanced - when the regression assessment should be paired with code-level risk review

Definition of Done

This skill is complete when:

• the change surface is explained clearly
• high, medium, and low regression areas are separated
• the must-retest pack is believable and prioritized
• open questions and blind spots are explicit
• the output can guide a tester or release lead immediately