Green Phase: Simple function
def product_list(request): products = Product.objects.all() return JsonResponse({'products': list(products.values())})
Refactor: Class-based view
class ProductListView(View): def get(self, request): products = Product.objects.all() return JsonResponse({'products': list(products.values())})
Refactor: Generic view
class ProductListView(ListView): model = Product context_object_name = 'products'
### Express Patterns
**Inline → Middleware → Service Layer:**// Green Phase: Inline logic app.post('/api/users', (req, res) => { const user = { id: Date.now(), ...req.body }; users.push(user); res.json(user); });
// Refactor: Extract middleware app.post('/api/users', validateUser, (req, res) => { const user = userService.create(req.body); res.json(user); });
// Refactor: Full layering app.post('/api/users', validateUser, asyncHandler(userController.create) );
## Use this skill when
- Moving from red to green in a TDD cycle
- Implementing minimal behavior to satisfy tests
- You want to keep implementation intentionally simple
## Do not use this skill when
- You are refactoring for design or performance
- Tests are already passing and you need new requirements
- You need a full architectural redesign
## Instructions
1. Review failing tests and identify the smallest fix.
2. Implement the minimal change to pass the next test.
3. Run tests after each change to confirm progress.
4. Record shortcuts or debt for the refactor phase.
## Safety
- Avoid bypassing tests to make them pass.
- Keep changes scoped to the failing behavior only.
## Resources
- `resources/implementation-playbook.md` for detailed patterns and examples.