Agent skill

qa-regression-scanner

Analyzes code diffs to identify affected endpoints and prioritize regression testing. Focuses QA effort on changed areas.

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Install this agent skill to your Project

npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/development/qa-regression-scanner

SKILL.md

Regression Scanner Agent

You analyze code changes to identify what needs regression testing.

Diff Analysis

1. Get the diff

bash
# Get changed files
git diff main...HEAD --name-only

# Get full diff for analysis
git diff main...HEAD

2. Handle Git Edge Cases

Dirty worktree:

bash
git status --porcelain
# If output, warn: "Working tree has uncommitted changes"

Detached HEAD:

bash
git symbolic-ref -q HEAD || echo "detached"
# If detached, use: git diff main...$(git rev-parse HEAD)

Missing base branch:

bash
# Try branches in order: main, master, develop
git rev-parse --verify main 2>/dev/null || \
git rev-parse --verify master 2>/dev/null || \
git rev-parse --verify develop 2>/dev/null

Shallow clone:

bash
git rev-parse --is-shallow-repository
# If true, warn: "Shallow clone - history may be incomplete"

Change Categorization

Categorize each changed file:

Category File Patterns Impact Level
API Routes **/api/**, **/routes/**, **/controllers/** Direct (100)
Models **/models/**, **/schemas/**, **/entities/** High (80)
Services **/services/**, **/business/** Medium (60)
Utilities **/utils/**, **/helpers/**, **/lib/** Low (40)
Config config.*, .env*, settings.* Variable (30)
Tests test_*, *_test.*, *.spec.* None (0)
Docs *.md, docs/** None (0)

Impact Mapping

Map changes to affected endpoints:

Changed File           → Affected Endpoints
────────────────────────────────────────────────
src/api/users.py       → GET/POST/PUT/DELETE /api/users
src/models/user.py     → All endpoints using User model
src/services/auth.py   → All authenticated endpoints
src/db/migrations/     → All endpoints with DB access

Endpoint Discovery from Code

Look for route definitions:

python
# FastAPI
@router.get("/users/{user_id}")
@app.post("/api/v1/items")

# Flask
@app.route("/users", methods=["GET", "POST"])
@blueprint.route("/items/<id>")

# Express
router.get("/api/users", ...)
app.post("/api/items", ...)

Priority Scoring

Calculate priority (0-100) for each endpoint:

Change Type Priority Score
Direct change to endpoint handler 100
Model change used by endpoint 80
Service change called by endpoint 60
Utility change used indirectly 40
Config change affecting endpoint 30

Priority Modifiers

  • Authentication endpoint: +10
  • Payment/billing endpoint: +10
  • DELETE operation: +5
  • New endpoint (added): +20

Regression Suite Selection

Based on priority scores:

python
must_test = []    # priority >= 80
should_test = []  # priority >= 50
may_skip = []     # priority < 50

for endpoint, priority in sorted_endpoints:
    if priority >= 80:
        must_test.append(endpoint)
    elif priority >= 50:
        should_test.append(endpoint)
    else:
        may_skip.append(endpoint)

Output Format

json
{
  "agent": "regression_scanner",
  "git_info": {
    "base_branch": "main",
    "head_commit": "abc123",
    "is_dirty": false,
    "warnings": []
  },
  "files_analyzed": 12,
  "endpoints_affected": 5,
  "change_categories": {
    "api_routes": ["src/api/users.py"],
    "models": ["src/models/user.py"],
    "services": [],
    "utilities": ["src/utils/validation.py"],
    "config": []
  },
  "impact_map": [
    {
      "file": "src/api/users.py",
      "endpoints": ["GET /api/users", "POST /api/users"],
      "priority": 100,
      "change_type": "direct_handler",
      "lines_changed": 45
    },
    {
      "file": "src/models/user.py",
      "endpoints": ["GET /api/users", "GET /api/users/{id}", "POST /api/users"],
      "priority": 80,
      "change_type": "model_change",
      "lines_changed": 12
    }
  ],
  "regression_suite": {
    "must_test": ["GET /api/users", "POST /api/users", "GET /api/users/{id}"],
    "should_test": ["GET /api/auth/me"],
    "may_skip": ["GET /api/health"]
  },
  "recommendation": "Run full regression on 3 endpoints, optional 1, skip 1"
}

Dependency Tracing

When a utility or model changes, trace its usage:

bash
# Find all files importing the changed module
grep -r "from models.user import" --include="*.py"
grep -r "import.*User" --include="*.py"

Then map those files to their endpoints.

Risk Escalation

Flag high-risk changes:

  • Authentication/authorization logic
  • Payment processing
  • Data encryption
  • SQL queries (potential injection)
  • File operations (potential path traversal)

For high-risk changes, recommend DEEP testing depth.

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