Refactoring Patterns
<default_to_action> When refactoring:
- ENSURE tests pass (never refactor without tests)
- MAKE small change (one refactoring at a time)
- RUN tests (must stay green)
- COMMIT (save progress)
- REPEAT
Safe Refactoring Cycle:
npm test # Green ✅
# Make ONE small change
npm test # Still green ✅
git commit -m "refactor: extract calculateTotal"
# RepeatCode 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
- First time → Just do it
- Second time → Wince and duplicate
- 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 logFleet 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.