proffesor-for-testing/refactoring-patterns

Refactoring Patterns

<default_to_action> When refactoring:

1. ENSURE tests pass (never refactor without tests)
2. MAKE small change (one refactoring at a time)
3. RUN tests (must stay green)
4. COMMIT (save progress)
5. REPEAT

Safe Refactoring Cycle:

npm test               # Green ✅
# Make ONE small change
npm test               # Still green ✅
git commit -m "refactor: extract calculateTotal"
# Repeat

Code Smells → Refactoring: | Smell | Refactoring | |-------|-------------| | Long method (>20 lines) | Extract Method | | Large class | Extract Class | | Long parameter list (>3) | Introduce Parameter Object | | Duplicated code | Extract Method/Class | | Complex conditional | Decompose Conditional | | Magic numbers | Named Constants | | Nested loops | Replace Loop with Pipeline |

NEVER REFACTOR:

• Without tests (write tests first)
• When deadline is tomorrow
• Code you don't understand
• Code that works and won't be touched </default_to_action>

Quick Reference Card

Common Refactorings

| Pattern | Before | After | |---------|--------|-------| | Extract Method | 50-line function | 5 small functions | | Extract Class | Class doing 5 things | 5 single-purpose classes | | Parameter Object | fn(a,b,c,d,e,f) | fn(options) | | Replace Conditional | if (type === 'a') {...} | Polymorphism | | Pipeline | Nested loops | .filter().map().reduce() |

The Rule of Three

1. First time → Just do it
2. Second time → Wince and duplicate
3. Third time → Refactor

---

Key Patterns

Extract Method

// Before: Long method
function processOrder(order) {
  // 50 lines of validation, calculation, saving, emailing...
}

// After: Clear responsibilities
function processOrder(order) {
  validateOrder(order);
  const pricing = calculatePricing(order);
  const saved = saveOrder(order, pricing);
  sendConfirmationEmail(saved);
  return saved;
}

Replace Loop with Pipeline

// Before
let results = [];
for (let item of items) {
  if (item.inStock) {
    results.push(item.name.toUpperCase());
  }
}

// After
const results = items
  .filter(item => item.inStock)
  .map(item => item.name.toUpperCase());

Decompose Conditional

// Before
if (order.total > 1000 && customer.isPremium && allInStock(order)) {
  return 'FREE_SHIPPING';
}

// After
function isEligibleForFreeShipping(order, customer) {
  return isLargeOrder(order) &&
         isPremiumCustomer(customer) &&
         allInStock(order);
}

---

Refactoring Anti-Patterns

| ❌ Anti-Pattern | Problem | ✅ Better | |-----------------|---------|-----------| | Without tests | No safety net | Write tests first | | Big bang | Rewrite everything | Small incremental steps | | For perfection | Endless tweaking | Good enough, move on | | Premature abstraction | Pattern not clear yet | Wait for Rule of Three | | During feature work | Mixed changes | Separate commits |

---

Agent Integration

// Detect code smells
const smells = await Task("Detect Code Smells", {
  source: 'src/services/',
  patterns: ['long-method', 'large-class', 'duplicate-code']
}, "qe-quality-analyzer");

// Safe refactoring with test verification
await Task("Verify Refactoring", {
  beforeCommit: 'abc123',
  afterCommit: 'def456',
  expectSameBehavior: true
}, "qe-test-executor");

---

Agent Coordination Hints

Memory Namespace

aqe/refactoring/
├── smells/*          - Detected code smells
├── suggestions/*     - Refactoring recommendations
├── verifications/*   - Behavior preservation checks
└── history/*         - Refactoring log

Fleet Coordination

const refactoringFleet = await FleetManager.coordinate({
  strategy: 'refactoring',
  agents: [
    'qe-quality-analyzer',   // Identify targets
    'qe-test-generator',     // Add safety tests
    'qe-test-executor',      // Verify behavior
    'qe-test-refactorer'     // TDD refactor phase
  ],
  topology: 'sequential'
});

---

Related Skills

• tdd-london-chicago - TDD refactor phase
• code-review-quality - Review refactored code
• xp-practices - Collective ownership

---

Remember

Refactoring is NOT:

• Adding features
• Fixing bugs
• Performance optimization
• Rewriting from scratch

Refactoring IS:

• Improving structure
• Making code clearer
• Reducing complexity
• Removing duplication
• Without changing behavior

Always have tests. Always take small steps. Always keep tests green.