Add Kiro skills (18 SKILL.md files) (#811)

Co-authored-by: Sungmin Hong <hsungmin@amazon.com>
This commit is contained in:
Himanshu Sharma
2026-03-22 21:55:45 -07:00
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---
name: agentic-engineering
description: >
Operate as an agentic engineer using eval-first execution, decomposition,
and cost-aware model routing. Use when AI agents perform most implementation
work and humans enforce quality and risk controls.
metadata:
origin: ECC
---
# Agentic Engineering
Use this skill for engineering workflows where AI agents perform most implementation work and humans enforce quality and risk controls.
## Operating Principles
1. Define completion criteria before execution.
2. Decompose work into agent-sized units.
3. Route model tiers by task complexity.
4. Measure with evals and regression checks.
## Eval-First Loop
1. Define capability eval and regression eval.
2. Run baseline and capture failure signatures.
3. Execute implementation.
4. Re-run evals and compare deltas.
**Example workflow:**
```
1. Write test that captures desired behavior (eval)
2. Run test → capture baseline failures
3. Implement feature
4. Re-run test → verify improvements
5. Check for regressions in other tests
```
## Task Decomposition
Apply the 15-minute unit rule:
- Each unit should be independently verifiable
- Each unit should have a single dominant risk
- Each unit should expose a clear done condition
**Good decomposition:**
```
Task: Add user authentication
├─ Unit 1: Add password hashing (15 min, security risk)
├─ Unit 2: Create login endpoint (15 min, API contract risk)
├─ Unit 3: Add session management (15 min, state risk)
└─ Unit 4: Protect routes with middleware (15 min, auth logic risk)
```
**Bad decomposition:**
```
Task: Add user authentication (2 hours, multiple risks)
```
## Model Routing
Choose model tier based on task complexity:
- **Haiku**: Classification, boilerplate transforms, narrow edits
- Example: Rename variable, add type annotation, format code
- **Sonnet**: Implementation and refactors
- Example: Implement feature, refactor module, write tests
- **Opus**: Architecture, root-cause analysis, multi-file invariants
- Example: Design system, debug complex issue, review architecture
**Cost discipline:** Escalate model tier only when lower tier fails with a clear reasoning gap.
## Session Strategy
- **Continue session** for closely-coupled units
- Example: Implementing related functions in same module
- **Start fresh session** after major phase transitions
- Example: Moving from implementation to testing
- **Compact after milestone completion**, not during active debugging
- Example: After feature complete, before starting next feature
## Review Focus for AI-Generated Code
Prioritize:
- Invariants and edge cases
- Error boundaries
- Security and auth assumptions
- Hidden coupling and rollout risk
Do not waste review cycles on style-only disagreements when automated format/lint already enforce style.
**Review checklist:**
- [ ] Edge cases handled (null, empty, boundary values)
- [ ] Error handling comprehensive
- [ ] Security assumptions validated
- [ ] No hidden coupling between modules
- [ ] Rollout risk assessed (breaking changes, migrations)
## Cost Discipline
Track per task:
- Model tier used
- Token estimate
- Retries needed
- Wall-clock time
- Success/failure outcome
**Example tracking:**
```
Task: Implement user login
Model: Sonnet
Tokens: ~5k input, ~2k output
Retries: 1 (initial implementation had auth bug)
Time: 8 minutes
Outcome: Success
```
## When to Use This Skill
- Managing AI-driven development workflows
- Planning agent task decomposition
- Optimizing model tier selection
- Implementing eval-first development
- Reviewing AI-generated code
- Tracking development costs
## Integration with Other Skills
- **tdd-workflow**: Combine with eval-first loop for test-driven development
- **verification-loop**: Use for continuous validation during implementation
- **search-first**: Apply before implementation to find existing solutions
- **coding-standards**: Reference during code review phase

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---
name: api-design
description: >
REST API design patterns including resource naming, status codes, pagination, filtering, error responses, versioning, and rate limiting for production APIs.
metadata:
origin: ECC
---
# API Design Patterns
Conventions and best practices for designing consistent, developer-friendly REST APIs.
## When to Activate
- Designing new API endpoints
- Reviewing existing API contracts
- Adding pagination, filtering, or sorting
- Implementing error handling for APIs
- Planning API versioning strategy
- Building public or partner-facing APIs
## Resource Design
### URL Structure
```
# Resources are nouns, plural, lowercase, kebab-case
GET /api/v1/users
GET /api/v1/users/:id
POST /api/v1/users
PUT /api/v1/users/:id
PATCH /api/v1/users/:id
DELETE /api/v1/users/:id
# Sub-resources for relationships
GET /api/v1/users/:id/orders
POST /api/v1/users/:id/orders
# Actions that don't map to CRUD (use verbs sparingly)
POST /api/v1/orders/:id/cancel
POST /api/v1/auth/login
POST /api/v1/auth/refresh
```
### Naming Rules
```
# GOOD
/api/v1/team-members # kebab-case for multi-word resources
/api/v1/orders?status=active # query params for filtering
/api/v1/users/123/orders # nested resources for ownership
# BAD
/api/v1/getUsers # verb in URL
/api/v1/user # singular (use plural)
/api/v1/team_members # snake_case in URLs
/api/v1/users/123/getOrders # verb in nested resource
```
## HTTP Methods and Status Codes
### Method Semantics
| Method | Idempotent | Safe | Use For |
|--------|-----------|------|---------|
| GET | Yes | Yes | Retrieve resources |
| POST | No | No | Create resources, trigger actions |
| PUT | Yes | No | Full replacement of a resource |
| PATCH | No* | No | Partial update of a resource |
| DELETE | Yes | No | Remove a resource |
*PATCH can be made idempotent with proper implementation
### Status Code Reference
```
# Success
200 OK — GET, PUT, PATCH (with response body)
201 Created — POST (include Location header)
204 No Content — DELETE, PUT (no response body)
# Client Errors
400 Bad Request — Validation failure, malformed JSON
401 Unauthorized — Missing or invalid authentication
403 Forbidden — Authenticated but not authorized
404 Not Found — Resource doesn't exist
409 Conflict — Duplicate entry, state conflict
422 Unprocessable Entity — Semantically invalid (valid JSON, bad data)
429 Too Many Requests — Rate limit exceeded
# Server Errors
500 Internal Server Error — Unexpected failure (never expose details)
502 Bad Gateway — Upstream service failed
503 Service Unavailable — Temporary overload, include Retry-After
```
### Common Mistakes
```
# BAD: 200 for everything
{ "status": 200, "success": false, "error": "Not found" }
# GOOD: Use HTTP status codes semantically
HTTP/1.1 404 Not Found
{ "error": { "code": "not_found", "message": "User not found" } }
# BAD: 500 for validation errors
# GOOD: 400 or 422 with field-level details
# BAD: 200 for created resources
# GOOD: 201 with Location header
HTTP/1.1 201 Created
Location: /api/v1/users/abc-123
```
## Response Format
### Success Response
```json
{
"data": {
"id": "abc-123",
"email": "alice@example.com",
"name": "Alice",
"created_at": "2025-01-15T10:30:00Z"
}
}
```
### Collection Response (with Pagination)
```json
{
"data": [
{ "id": "abc-123", "name": "Alice" },
{ "id": "def-456", "name": "Bob" }
],
"meta": {
"total": 142,
"page": 1,
"per_page": 20,
"total_pages": 8
},
"links": {
"self": "/api/v1/users?page=1&per_page=20",
"next": "/api/v1/users?page=2&per_page=20",
"last": "/api/v1/users?page=8&per_page=20"
}
}
```
### Error Response
```json
{
"error": {
"code": "validation_error",
"message": "Request validation failed",
"details": [
{
"field": "email",
"message": "Must be a valid email address",
"code": "invalid_format"
},
{
"field": "age",
"message": "Must be between 0 and 150",
"code": "out_of_range"
}
]
}
}
```
### Response Envelope Variants
```typescript
// Option A: Envelope with data wrapper (recommended for public APIs)
interface ApiResponse<T> {
data: T;
meta?: PaginationMeta;
links?: PaginationLinks;
}
interface ApiError {
error: {
code: string;
message: string;
details?: FieldError[];
};
}
// Option B: Flat response (simpler, common for internal APIs)
// Success: just return the resource directly
// Error: return error object
// Distinguish by HTTP status code
```
## Pagination
### Offset-Based (Simple)
```
GET /api/v1/users?page=2&per_page=20
# Implementation
SELECT * FROM users
ORDER BY created_at DESC
LIMIT 20 OFFSET 20;
```
**Pros:** Easy to implement, supports "jump to page N"
**Cons:** Slow on large offsets (OFFSET 100000), inconsistent with concurrent inserts
### Cursor-Based (Scalable)
```
GET /api/v1/users?cursor=eyJpZCI6MTIzfQ&limit=20
# Implementation
SELECT * FROM users
WHERE id > :cursor_id
ORDER BY id ASC
LIMIT 21; -- fetch one extra to determine has_next
```
```json
{
"data": [...],
"meta": {
"has_next": true,
"next_cursor": "eyJpZCI6MTQzfQ"
}
}
```
**Pros:** Consistent performance regardless of position, stable with concurrent inserts
**Cons:** Cannot jump to arbitrary page, cursor is opaque
### When to Use Which
| Use Case | Pagination Type |
|----------|----------------|
| Admin dashboards, small datasets (<10K) | Offset |
| Infinite scroll, feeds, large datasets | Cursor |
| Public APIs | Cursor (default) with offset (optional) |
| Search results | Offset (users expect page numbers) |
## Filtering, Sorting, and Search
### Filtering
```
# Simple equality
GET /api/v1/orders?status=active&customer_id=abc-123
# Comparison operators (use bracket notation)
GET /api/v1/products?price[gte]=10&price[lte]=100
GET /api/v1/orders?created_at[after]=2025-01-01
# Multiple values (comma-separated)
GET /api/v1/products?category=electronics,clothing
# Nested fields (dot notation)
GET /api/v1/orders?customer.country=US
```
### Sorting
```
# Single field (prefix - for descending)
GET /api/v1/products?sort=-created_at
# Multiple fields (comma-separated)
GET /api/v1/products?sort=-featured,price,-created_at
```
### Full-Text Search
```
# Search query parameter
GET /api/v1/products?q=wireless+headphones
# Field-specific search
GET /api/v1/users?email=alice
```
### Sparse Fieldsets
```
# Return only specified fields (reduces payload)
GET /api/v1/users?fields=id,name,email
GET /api/v1/orders?fields=id,total,status&include=customer.name
```
## Authentication and Authorization
### Token-Based Auth
```
# Bearer token in Authorization header
GET /api/v1/users
Authorization: Bearer eyJhbGciOiJIUzI1NiIs...
# API key (for server-to-server)
GET /api/v1/data
X-API-Key: sk_live_abc123
```
### Authorization Patterns
```typescript
// Resource-level: check ownership
app.get("/api/v1/orders/:id", async (req, res) => {
const order = await Order.findById(req.params.id);
if (!order) return res.status(404).json({ error: { code: "not_found" } });
if (order.userId !== req.user.id) return res.status(403).json({ error: { code: "forbidden" } });
return res.json({ data: order });
});
// Role-based: check permissions
app.delete("/api/v1/users/:id", requireRole("admin"), async (req, res) => {
await User.delete(req.params.id);
return res.status(204).send();
});
```
## Rate Limiting
### Headers
```
HTTP/1.1 200 OK
X-RateLimit-Limit: 100
X-RateLimit-Remaining: 95
X-RateLimit-Reset: 1640000000
# When exceeded
HTTP/1.1 429 Too Many Requests
Retry-After: 60
{
"error": {
"code": "rate_limit_exceeded",
"message": "Rate limit exceeded. Try again in 60 seconds."
}
}
```
### Rate Limit Tiers
| Tier | Limit | Window | Use Case |
|------|-------|--------|----------|
| Anonymous | 30/min | Per IP | Public endpoints |
| Authenticated | 100/min | Per user | Standard API access |
| Premium | 1000/min | Per API key | Paid API plans |
| Internal | 10000/min | Per service | Service-to-service |
## Versioning
### URL Path Versioning (Recommended)
```
/api/v1/users
/api/v2/users
```
**Pros:** Explicit, easy to route, cacheable
**Cons:** URL changes between versions
### Header Versioning
```
GET /api/users
Accept: application/vnd.myapp.v2+json
```
**Pros:** Clean URLs
**Cons:** Harder to test, easy to forget
### Versioning Strategy
```
1. Start with /api/v1/ — don't version until you need to
2. Maintain at most 2 active versions (current + previous)
3. Deprecation timeline:
- Announce deprecation (6 months notice for public APIs)
- Add Sunset header: Sunset: Sat, 01 Jan 2026 00:00:00 GMT
- Return 410 Gone after sunset date
4. Non-breaking changes don't need a new version:
- Adding new fields to responses
- Adding new optional query parameters
- Adding new endpoints
5. Breaking changes require a new version:
- Removing or renaming fields
- Changing field types
- Changing URL structure
- Changing authentication method
```
## Implementation Patterns
### TypeScript (Next.js API Route)
```typescript
import { z } from "zod";
import { NextRequest, NextResponse } from "next/server";
const createUserSchema = z.object({
email: z.string().email(),
name: z.string().min(1).max(100),
});
export async function POST(req: NextRequest) {
const body = await req.json();
const parsed = createUserSchema.safeParse(body);
if (!parsed.success) {
return NextResponse.json({
error: {
code: "validation_error",
message: "Request validation failed",
details: parsed.error.issues.map(i => ({
field: i.path.join("."),
message: i.message,
code: i.code,
})),
},
}, { status: 422 });
}
const user = await createUser(parsed.data);
return NextResponse.json(
{ data: user },
{
status: 201,
headers: { Location: `/api/v1/users/${user.id}` },
},
);
}
```
### Python (Django REST Framework)
```python
from rest_framework import serializers, viewsets, status
from rest_framework.response import Response
class CreateUserSerializer(serializers.Serializer):
email = serializers.EmailField()
name = serializers.CharField(max_length=100)
class UserSerializer(serializers.ModelSerializer):
class Meta:
model = User
fields = ["id", "email", "name", "created_at"]
class UserViewSet(viewsets.ModelViewSet):
serializer_class = UserSerializer
permission_classes = [IsAuthenticated]
def get_serializer_class(self):
if self.action == "create":
return CreateUserSerializer
return UserSerializer
def create(self, request):
serializer = CreateUserSerializer(data=request.data)
serializer.is_valid(raise_exception=True)
user = UserService.create(**serializer.validated_data)
return Response(
{"data": UserSerializer(user).data},
status=status.HTTP_201_CREATED,
headers={"Location": f"/api/v1/users/{user.id}"},
)
```
### Go (net/http)
```go
func (h *UserHandler) CreateUser(w http.ResponseWriter, r *http.Request) {
var req CreateUserRequest
if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
writeError(w, http.StatusBadRequest, "invalid_json", "Invalid request body")
return
}
if err := req.Validate(); err != nil {
writeError(w, http.StatusUnprocessableEntity, "validation_error", err.Error())
return
}
user, err := h.service.Create(r.Context(), req)
if err != nil {
switch {
case errors.Is(err, domain.ErrEmailTaken):
writeError(w, http.StatusConflict, "email_taken", "Email already registered")
default:
writeError(w, http.StatusInternalServerError, "internal_error", "Internal error")
}
return
}
w.Header().Set("Location", fmt.Sprintf("/api/v1/users/%s", user.ID))
writeJSON(w, http.StatusCreated, map[string]any{"data": user})
}
```
## API Design Checklist
Before shipping a new endpoint:
- [ ] Resource URL follows naming conventions (plural, kebab-case, no verbs)
- [ ] Correct HTTP method used (GET for reads, POST for creates, etc.)
- [ ] Appropriate status codes returned (not 200 for everything)
- [ ] Input validated with schema (Zod, Pydantic, Bean Validation)
- [ ] Error responses follow standard format with codes and messages
- [ ] Pagination implemented for list endpoints (cursor or offset)
- [ ] Authentication required (or explicitly marked as public)
- [ ] Authorization checked (user can only access their own resources)
- [ ] Rate limiting configured
- [ ] Response does not leak internal details (stack traces, SQL errors)
- [ ] Consistent naming with existing endpoints (camelCase vs snake_case)
- [ ] Documented (OpenAPI/Swagger spec updated)

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---
name: backend-patterns
description: >
Backend architecture patterns, API design, database optimization, and server-side best practices for Node.js, Express, and Next.js API routes.
metadata:
origin: ECC
---
# Backend Development Patterns
Backend architecture patterns and best practices for scalable server-side applications.
## When to Activate
- Designing REST or GraphQL API endpoints
- Implementing repository, service, or controller layers
- Optimizing database queries (N+1, indexing, connection pooling)
- Adding caching (Redis, in-memory, HTTP cache headers)
- Setting up background jobs or async processing
- Structuring error handling and validation for APIs
- Building middleware (auth, logging, rate limiting)
## API Design Patterns
### RESTful API Structure
```typescript
// ✅ Resource-based URLs
GET /api/markets # List resources
GET /api/markets/:id # Get single resource
POST /api/markets # Create resource
PUT /api/markets/:id # Replace resource
PATCH /api/markets/:id # Update resource
DELETE /api/markets/:id # Delete resource
// ✅ Query parameters for filtering, sorting, pagination
GET /api/markets?status=active&sort=volume&limit=20&offset=0
```
### Repository Pattern
```typescript
// Abstract data access logic
interface MarketRepository {
findAll(filters?: MarketFilters): Promise<Market[]>
findById(id: string): Promise<Market | null>
create(data: CreateMarketDto): Promise<Market>
update(id: string, data: UpdateMarketDto): Promise<Market>
delete(id: string): Promise<void>
}
class SupabaseMarketRepository implements MarketRepository {
async findAll(filters?: MarketFilters): Promise<Market[]> {
let query = supabase.from('markets').select('*')
if (filters?.status) {
query = query.eq('status', filters.status)
}
if (filters?.limit) {
query = query.limit(filters.limit)
}
const { data, error } = await query
if (error) throw new Error(error.message)
return data
}
// Other methods...
}
```
### Service Layer Pattern
```typescript
// Business logic separated from data access
class MarketService {
constructor(private marketRepo: MarketRepository) {}
async searchMarkets(query: string, limit: number = 10): Promise<Market[]> {
// Business logic
const embedding = await generateEmbedding(query)
const results = await this.vectorSearch(embedding, limit)
// Fetch full data
const markets = await this.marketRepo.findByIds(results.map(r => r.id))
// Sort by similarity
return markets.sort((a, b) => {
const scoreA = results.find(r => r.id === a.id)?.score || 0
const scoreB = results.find(r => r.id === b.id)?.score || 0
return scoreA - scoreB
})
}
private async vectorSearch(embedding: number[], limit: number) {
// Vector search implementation
}
}
```
### Middleware Pattern
```typescript
// Request/response processing pipeline
export function withAuth(handler: NextApiHandler): NextApiHandler {
return async (req, res) => {
const token = req.headers.authorization?.replace('Bearer ', '')
if (!token) {
return res.status(401).json({ error: 'Unauthorized' })
}
try {
const user = await verifyToken(token)
req.user = user
return handler(req, res)
} catch (error) {
return res.status(401).json({ error: 'Invalid token' })
}
}
}
// Usage
export default withAuth(async (req, res) => {
// Handler has access to req.user
})
```
## Database Patterns
### Query Optimization
```typescript
// ✅ GOOD: Select only needed columns
const { data } = await supabase
.from('markets')
.select('id, name, status, volume')
.eq('status', 'active')
.order('volume', { ascending: false })
.limit(10)
// ❌ BAD: Select everything
const { data } = await supabase
.from('markets')
.select('*')
```
### N+1 Query Prevention
```typescript
// ❌ BAD: N+1 query problem
const markets = await getMarkets()
for (const market of markets) {
market.creator = await getUser(market.creator_id) // N queries
}
// ✅ GOOD: Batch fetch
const markets = await getMarkets()
const creatorIds = markets.map(m => m.creator_id)
const creators = await getUsers(creatorIds) // 1 query
const creatorMap = new Map(creators.map(c => [c.id, c]))
markets.forEach(market => {
market.creator = creatorMap.get(market.creator_id)
})
```
### Transaction Pattern
```typescript
async function createMarketWithPosition(
marketData: CreateMarketDto,
positionData: CreatePositionDto
) {
// Use Supabase transaction
const { data, error } = await supabase.rpc('create_market_with_position', {
market_data: marketData,
position_data: positionData
})
if (error) throw new Error('Transaction failed')
return data
}
// SQL function in Supabase
CREATE OR REPLACE FUNCTION create_market_with_position(
market_data jsonb,
position_data jsonb
)
RETURNS jsonb
LANGUAGE plpgsql
AS $
BEGIN
-- Start transaction automatically
INSERT INTO markets VALUES (market_data);
INSERT INTO positions VALUES (position_data);
RETURN jsonb_build_object('success', true);
EXCEPTION
WHEN OTHERS THEN
-- Rollback happens automatically
RETURN jsonb_build_object('success', false, 'error', SQLERRM);
END;
$;
```
## Caching Strategies
### Redis Caching Layer
```typescript
class CachedMarketRepository implements MarketRepository {
constructor(
private baseRepo: MarketRepository,
private redis: RedisClient
) {}
async findById(id: string): Promise<Market | null> {
// Check cache first
const cached = await this.redis.get(`market:${id}`)
if (cached) {
return JSON.parse(cached)
}
// Cache miss - fetch from database
const market = await this.baseRepo.findById(id)
if (market) {
// Cache for 5 minutes
await this.redis.setex(`market:${id}`, 300, JSON.stringify(market))
}
return market
}
async invalidateCache(id: string): Promise<void> {
await this.redis.del(`market:${id}`)
}
}
```
### Cache-Aside Pattern
```typescript
async function getMarketWithCache(id: string): Promise<Market> {
const cacheKey = `market:${id}`
// Try cache
const cached = await redis.get(cacheKey)
if (cached) return JSON.parse(cached)
// Cache miss - fetch from DB
const market = await db.markets.findUnique({ where: { id } })
if (!market) throw new Error('Market not found')
// Update cache
await redis.setex(cacheKey, 300, JSON.stringify(market))
return market
}
```
## Error Handling Patterns
### Centralized Error Handler
```typescript
class ApiError extends Error {
constructor(
public statusCode: number,
public message: string,
public isOperational = true
) {
super(message)
Object.setPrototypeOf(this, ApiError.prototype)
}
}
export function errorHandler(error: unknown, req: Request): Response {
if (error instanceof ApiError) {
return NextResponse.json({
success: false,
error: error.message
}, { status: error.statusCode })
}
if (error instanceof z.ZodError) {
return NextResponse.json({
success: false,
error: 'Validation failed',
details: error.errors
}, { status: 400 })
}
// Log unexpected errors
console.error('Unexpected error:', error)
return NextResponse.json({
success: false,
error: 'Internal server error'
}, { status: 500 })
}
// Usage
export async function GET(request: Request) {
try {
const data = await fetchData()
return NextResponse.json({ success: true, data })
} catch (error) {
return errorHandler(error, request)
}
}
```
### Retry with Exponential Backoff
```typescript
async function fetchWithRetry<T>(
fn: () => Promise<T>,
maxRetries = 3
): Promise<T> {
let lastError: Error
for (let i = 0; i < maxRetries; i++) {
try {
return await fn()
} catch (error) {
lastError = error as Error
if (i < maxRetries - 1) {
// Exponential backoff: 1s, 2s, 4s
const delay = Math.pow(2, i) * 1000
await new Promise(resolve => setTimeout(resolve, delay))
}
}
}
throw lastError!
}
// Usage
const data = await fetchWithRetry(() => fetchFromAPI())
```
## Authentication & Authorization
### JWT Token Validation
```typescript
import jwt from 'jsonwebtoken'
interface JWTPayload {
userId: string
email: string
role: 'admin' | 'user'
}
export function verifyToken(token: string): JWTPayload {
try {
const payload = jwt.verify(token, process.env.JWT_SECRET!) as JWTPayload
return payload
} catch (error) {
throw new ApiError(401, 'Invalid token')
}
}
export async function requireAuth(request: Request) {
const token = request.headers.get('authorization')?.replace('Bearer ', '')
if (!token) {
throw new ApiError(401, 'Missing authorization token')
}
return verifyToken(token)
}
// Usage in API route
export async function GET(request: Request) {
const user = await requireAuth(request)
const data = await getDataForUser(user.userId)
return NextResponse.json({ success: true, data })
}
```
### Role-Based Access Control
```typescript
type Permission = 'read' | 'write' | 'delete' | 'admin'
interface User {
id: string
role: 'admin' | 'moderator' | 'user'
}
const rolePermissions: Record<User['role'], Permission[]> = {
admin: ['read', 'write', 'delete', 'admin'],
moderator: ['read', 'write', 'delete'],
user: ['read', 'write']
}
export function hasPermission(user: User, permission: Permission): boolean {
return rolePermissions[user.role].includes(permission)
}
export function requirePermission(permission: Permission) {
return (handler: (request: Request, user: User) => Promise<Response>) => {
return async (request: Request) => {
const user = await requireAuth(request)
if (!hasPermission(user, permission)) {
throw new ApiError(403, 'Insufficient permissions')
}
return handler(request, user)
}
}
}
// Usage - HOF wraps the handler
export const DELETE = requirePermission('delete')(
async (request: Request, user: User) => {
// Handler receives authenticated user with verified permission
return new Response('Deleted', { status: 200 })
}
)
```
## Rate Limiting
### Simple In-Memory Rate Limiter
```typescript
class RateLimiter {
private requests = new Map<string, number[]>()
async checkLimit(
identifier: string,
maxRequests: number,
windowMs: number
): Promise<boolean> {
const now = Date.now()
const requests = this.requests.get(identifier) || []
// Remove old requests outside window
const recentRequests = requests.filter(time => now - time < windowMs)
if (recentRequests.length >= maxRequests) {
return false // Rate limit exceeded
}
// Add current request
recentRequests.push(now)
this.requests.set(identifier, recentRequests)
return true
}
}
const limiter = new RateLimiter()
export async function GET(request: Request) {
const ip = request.headers.get('x-forwarded-for') || 'unknown'
const allowed = await limiter.checkLimit(ip, 100, 60000) // 100 req/min
if (!allowed) {
return NextResponse.json({
error: 'Rate limit exceeded'
}, { status: 429 })
}
// Continue with request
}
```
## Background Jobs & Queues
### Simple Queue Pattern
```typescript
class JobQueue<T> {
private queue: T[] = []
private processing = false
async add(job: T): Promise<void> {
this.queue.push(job)
if (!this.processing) {
this.process()
}
}
private async process(): Promise<void> {
this.processing = true
while (this.queue.length > 0) {
const job = this.queue.shift()!
try {
await this.execute(job)
} catch (error) {
console.error('Job failed:', error)
}
}
this.processing = false
}
private async execute(job: T): Promise<void> {
// Job execution logic
}
}
// Usage for indexing markets
interface IndexJob {
marketId: string
}
const indexQueue = new JobQueue<IndexJob>()
export async function POST(request: Request) {
const { marketId } = await request.json()
// Add to queue instead of blocking
await indexQueue.add({ marketId })
return NextResponse.json({ success: true, message: 'Job queued' })
}
```
## Logging & Monitoring
### Structured Logging
```typescript
interface LogContext {
userId?: string
requestId?: string
method?: string
path?: string
[key: string]: unknown
}
class Logger {
log(level: 'info' | 'warn' | 'error', message: string, context?: LogContext) {
const entry = {
timestamp: new Date().toISOString(),
level,
message,
...context
}
console.log(JSON.stringify(entry))
}
info(message: string, context?: LogContext) {
this.log('info', message, context)
}
warn(message: string, context?: LogContext) {
this.log('warn', message, context)
}
error(message: string, error: Error, context?: LogContext) {
this.log('error', message, {
...context,
error: error.message,
stack: error.stack
})
}
}
const logger = new Logger()
// Usage
export async function GET(request: Request) {
const requestId = crypto.randomUUID()
logger.info('Fetching markets', {
requestId,
method: 'GET',
path: '/api/markets'
})
try {
const markets = await fetchMarkets()
return NextResponse.json({ success: true, data: markets })
} catch (error) {
logger.error('Failed to fetch markets', error as Error, { requestId })
return NextResponse.json({ error: 'Internal error' }, { status: 500 })
}
}
```
**Remember**: Backend patterns enable scalable, maintainable server-side applications. Choose patterns that fit your complexity level.

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---
name: coding-standards
description: >
Universal coding standards, best practices, and patterns for TypeScript, JavaScript, React, and Node.js development.
metadata:
origin: ECC
---
# Coding Standards & Best Practices
Universal coding standards applicable across all projects.
## When to Activate
- Starting a new project or module
- Reviewing code for quality and maintainability
- Refactoring existing code to follow conventions
- Enforcing naming, formatting, or structural consistency
- Setting up linting, formatting, or type-checking rules
- Onboarding new contributors to coding conventions
## Code Quality Principles
### 1. Readability First
- Code is read more than written
- Clear variable and function names
- Self-documenting code preferred over comments
- Consistent formatting
### 2. KISS (Keep It Simple, Stupid)
- Simplest solution that works
- Avoid over-engineering
- No premature optimization
- Easy to understand > clever code
### 3. DRY (Don't Repeat Yourself)
- Extract common logic into functions
- Create reusable components
- Share utilities across modules
- Avoid copy-paste programming
### 4. YAGNI (You Aren't Gonna Need It)
- Don't build features before they're needed
- Avoid speculative generality
- Add complexity only when required
- Start simple, refactor when needed
## TypeScript/JavaScript Standards
### Variable Naming
```typescript
// ✅ GOOD: Descriptive names
const marketSearchQuery = 'election'
const isUserAuthenticated = true
const totalRevenue = 1000
// ❌ BAD: Unclear names
const q = 'election'
const flag = true
const x = 1000
```
### Function Naming
```typescript
// ✅ GOOD: Verb-noun pattern
async function fetchMarketData(marketId: string) { }
function calculateSimilarity(a: number[], b: number[]) { }
function isValidEmail(email: string): boolean { }
// ❌ BAD: Unclear or noun-only
async function market(id: string) { }
function similarity(a, b) { }
function email(e) { }
```
### Immutability Pattern (CRITICAL)
```typescript
// ✅ ALWAYS use spread operator
const updatedUser = {
...user,
name: 'New Name'
}
const updatedArray = [...items, newItem]
// ❌ NEVER mutate directly
user.name = 'New Name' // BAD
items.push(newItem) // BAD
```
### Error Handling
```typescript
// ✅ GOOD: Comprehensive error handling
async function fetchData(url: string) {
try {
const response = await fetch(url)
if (!response.ok) {
throw new Error(`HTTP ${response.status}: ${response.statusText}`)
}
return await response.json()
} catch (error) {
console.error('Fetch failed:', error)
throw new Error('Failed to fetch data')
}
}
// ❌ BAD: No error handling
async function fetchData(url) {
const response = await fetch(url)
return response.json()
}
```
### Async/Await Best Practices
```typescript
// ✅ GOOD: Parallel execution when possible
const [users, markets, stats] = await Promise.all([
fetchUsers(),
fetchMarkets(),
fetchStats()
])
// ❌ BAD: Sequential when unnecessary
const users = await fetchUsers()
const markets = await fetchMarkets()
const stats = await fetchStats()
```
### Type Safety
```typescript
// ✅ GOOD: Proper types
interface Market {
id: string
name: string
status: 'active' | 'resolved' | 'closed'
created_at: Date
}
function getMarket(id: string): Promise<Market> {
// Implementation
}
// ❌ BAD: Using 'any'
function getMarket(id: any): Promise<any> {
// Implementation
}
```
## React Best Practices
### Component Structure
```typescript
// ✅ GOOD: Functional component with types
interface ButtonProps {
children: React.ReactNode
onClick: () => void
disabled?: boolean
variant?: 'primary' | 'secondary'
}
export function Button({
children,
onClick,
disabled = false,
variant = 'primary'
}: ButtonProps) {
return (
<button
onClick={onClick}
disabled={disabled}
className={`btn btn-${variant}`}
>
{children}
</button>
)
}
// ❌ BAD: No types, unclear structure
export function Button(props) {
return <button onClick={props.onClick}>{props.children}</button>
}
```
### Custom Hooks
```typescript
// ✅ GOOD: Reusable custom hook
export function useDebounce<T>(value: T, delay: number): T {
const [debouncedValue, setDebouncedValue] = useState<T>(value)
useEffect(() => {
const handler = setTimeout(() => {
setDebouncedValue(value)
}, delay)
return () => clearTimeout(handler)
}, [value, delay])
return debouncedValue
}
// Usage
const debouncedQuery = useDebounce(searchQuery, 500)
```
### State Management
```typescript
// ✅ GOOD: Proper state updates
const [count, setCount] = useState(0)
// Functional update for state based on previous state
setCount(prev => prev + 1)
// ❌ BAD: Direct state reference
setCount(count + 1) // Can be stale in async scenarios
```
### Conditional Rendering
```typescript
// ✅ GOOD: Clear conditional rendering
{isLoading && <Spinner />}
{error && <ErrorMessage error={error} />}
{data && <DataDisplay data={data} />}
// ❌ BAD: Ternary hell
{isLoading ? <Spinner /> : error ? <ErrorMessage error={error} /> : data ? <DataDisplay data={data} /> : null}
```
## API Design Standards
### REST API Conventions
```
GET /api/markets # List all markets
GET /api/markets/:id # Get specific market
POST /api/markets # Create new market
PUT /api/markets/:id # Update market (full)
PATCH /api/markets/:id # Update market (partial)
DELETE /api/markets/:id # Delete market
# Query parameters for filtering
GET /api/markets?status=active&limit=10&offset=0
```
### Response Format
```typescript
// ✅ GOOD: Consistent response structure
interface ApiResponse<T> {
success: boolean
data?: T
error?: string
meta?: {
total: number
page: number
limit: number
}
}
// Success response
return NextResponse.json({
success: true,
data: markets,
meta: { total: 100, page: 1, limit: 10 }
})
// Error response
return NextResponse.json({
success: false,
error: 'Invalid request'
}, { status: 400 })
```
### Input Validation
```typescript
import { z } from 'zod'
// ✅ GOOD: Schema validation
const CreateMarketSchema = z.object({
name: z.string().min(1).max(200),
description: z.string().min(1).max(2000),
endDate: z.string().datetime(),
categories: z.array(z.string()).min(1)
})
export async function POST(request: Request) {
const body = await request.json()
try {
const validated = CreateMarketSchema.parse(body)
// Proceed with validated data
} catch (error) {
if (error instanceof z.ZodError) {
return NextResponse.json({
success: false,
error: 'Validation failed',
details: error.errors
}, { status: 400 })
}
}
}
```
## File Organization
### Project Structure
```
src/
├── app/ # Next.js App Router
│ ├── api/ # API routes
│ ├── markets/ # Market pages
│ └── (auth)/ # Auth pages (route groups)
├── components/ # React components
│ ├── ui/ # Generic UI components
│ ├── forms/ # Form components
│ └── layouts/ # Layout components
├── hooks/ # Custom React hooks
├── lib/ # Utilities and configs
│ ├── api/ # API clients
│ ├── utils/ # Helper functions
│ └── constants/ # Constants
├── types/ # TypeScript types
└── styles/ # Global styles
```
### File Naming
```
components/Button.tsx # PascalCase for components
hooks/useAuth.ts # camelCase with 'use' prefix
lib/formatDate.ts # camelCase for utilities
types/market.types.ts # camelCase with .types suffix
```
## Comments & Documentation
### When to Comment
```typescript
// ✅ GOOD: Explain WHY, not WHAT
// Use exponential backoff to avoid overwhelming the API during outages
const delay = Math.min(1000 * Math.pow(2, retryCount), 30000)
// Deliberately using mutation here for performance with large arrays
items.push(newItem)
// ❌ BAD: Stating the obvious
// Increment counter by 1
count++
// Set name to user's name
name = user.name
```
### JSDoc for Public APIs
```typescript
/**
* Searches markets using semantic similarity.
*
* @param query - Natural language search query
* @param limit - Maximum number of results (default: 10)
* @returns Array of markets sorted by similarity score
* @throws {Error} If OpenAI API fails or Redis unavailable
*
* @example
* ```typescript
* const results = await searchMarkets('election', 5)
* console.log(results[0].name) // "Trump vs Biden"
* ```
*/
export async function searchMarkets(
query: string,
limit: number = 10
): Promise<Market[]> {
// Implementation
}
```
## Performance Best Practices
### Memoization
```typescript
import { useMemo, useCallback } from 'react'
// ✅ GOOD: Memoize expensive computations
const sortedMarkets = useMemo(() => {
return markets.sort((a, b) => b.volume - a.volume)
}, [markets])
// ✅ GOOD: Memoize callbacks
const handleSearch = useCallback((query: string) => {
setSearchQuery(query)
}, [])
```
### Lazy Loading
```typescript
import { lazy, Suspense } from 'react'
// ✅ GOOD: Lazy load heavy components
const HeavyChart = lazy(() => import('./HeavyChart'))
export function Dashboard() {
return (
<Suspense fallback={<Spinner />}>
<HeavyChart />
</Suspense>
)
}
```
### Database Queries
```typescript
// ✅ GOOD: Select only needed columns
const { data } = await supabase
.from('markets')
.select('id, name, status')
.limit(10)
// ❌ BAD: Select everything
const { data } = await supabase
.from('markets')
.select('*')
```
## Testing Standards
### Test Structure (AAA Pattern)
```typescript
test('calculates similarity correctly', () => {
// Arrange
const vector1 = [1, 0, 0]
const vector2 = [0, 1, 0]
// Act
const similarity = calculateCosineSimilarity(vector1, vector2)
// Assert
expect(similarity).toBe(0)
})
```
### Test Naming
```typescript
// ✅ GOOD: Descriptive test names
test('returns empty array when no markets match query', () => { })
test('throws error when OpenAI API key is missing', () => { })
test('falls back to substring search when Redis unavailable', () => { })
// ❌ BAD: Vague test names
test('works', () => { })
test('test search', () => { })
```
## Code Smell Detection
Watch for these anti-patterns:
### 1. Long Functions
```typescript
// ❌ BAD: Function > 50 lines
function processMarketData() {
// 100 lines of code
}
// ✅ GOOD: Split into smaller functions
function processMarketData() {
const validated = validateData()
const transformed = transformData(validated)
return saveData(transformed)
}
```
### 2. Deep Nesting
```typescript
// ❌ BAD: 5+ levels of nesting
if (user) {
if (user.isAdmin) {
if (market) {
if (market.isActive) {
if (hasPermission) {
// Do something
}
}
}
}
}
// ✅ GOOD: Early returns
if (!user) return
if (!user.isAdmin) return
if (!market) return
if (!market.isActive) return
if (!hasPermission) return
// Do something
```
### 3. Magic Numbers
```typescript
// ❌ BAD: Unexplained numbers
if (retryCount > 3) { }
setTimeout(callback, 500)
// ✅ GOOD: Named constants
const MAX_RETRIES = 3
const DEBOUNCE_DELAY_MS = 500
if (retryCount > MAX_RETRIES) { }
setTimeout(callback, DEBOUNCE_DELAY_MS)
```
**Remember**: Code quality is not negotiable. Clear, maintainable code enables rapid development and confident refactoring.

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---
name: database-migrations
description: >
Database migration best practices for schema changes, data migrations, rollbacks,
and zero-downtime deployments across PostgreSQL, MySQL, and common ORMs (Prisma,
Drizzle, Django, TypeORM, golang-migrate). Use when planning or implementing
database schema changes.
metadata:
origin: ECC
---
# Database Migration Patterns
Safe, reversible database schema changes for production systems.
## When to Activate
- Creating or altering database tables
- Adding/removing columns or indexes
- Running data migrations (backfill, transform)
- Planning zero-downtime schema changes
- Setting up migration tooling for a new project
## Core Principles
1. **Every change is a migration** — never alter production databases manually
2. **Migrations are forward-only in production** — rollbacks use new forward migrations
3. **Schema and data migrations are separate** — never mix DDL and DML in one migration
4. **Test migrations against production-sized data** — a migration that works on 100 rows may lock on 10M
5. **Migrations are immutable once deployed** — never edit a migration that has run in production
## Migration Safety Checklist
Before applying any migration:
- [ ] Migration has both UP and DOWN (or is explicitly marked irreversible)
- [ ] No full table locks on large tables (use concurrent operations)
- [ ] New columns have defaults or are nullable (never add NOT NULL without default)
- [ ] Indexes created concurrently (not inline with CREATE TABLE for existing tables)
- [ ] Data backfill is a separate migration from schema change
- [ ] Tested against a copy of production data
- [ ] Rollback plan documented
## PostgreSQL Patterns
### Adding a Column Safely
```sql
-- GOOD: Nullable column, no lock
ALTER TABLE users ADD COLUMN avatar_url TEXT;
-- GOOD: Column with default (Postgres 11+ is instant, no rewrite)
ALTER TABLE users ADD COLUMN is_active BOOLEAN NOT NULL DEFAULT true;
-- BAD: NOT NULL without default on existing table (requires full rewrite)
ALTER TABLE users ADD COLUMN role TEXT NOT NULL;
-- This locks the table and rewrites every row
```
### Adding an Index Without Downtime
```sql
-- BAD: Blocks writes on large tables
CREATE INDEX idx_users_email ON users (email);
-- GOOD: Non-blocking, allows concurrent writes
CREATE INDEX CONCURRENTLY idx_users_email ON users (email);
-- Note: CONCURRENTLY cannot run inside a transaction block
-- Most migration tools need special handling for this
```
### Renaming a Column (Zero-Downtime)
Never rename directly in production. Use the expand-contract pattern:
```sql
-- Step 1: Add new column (migration 001)
ALTER TABLE users ADD COLUMN display_name TEXT;
-- Step 2: Backfill data (migration 002, data migration)
UPDATE users SET display_name = username WHERE display_name IS NULL;
-- Step 3: Update application code to read/write both columns
-- Deploy application changes
-- Step 4: Stop writing to old column, drop it (migration 003)
ALTER TABLE users DROP COLUMN username;
```
### Removing a Column Safely
```sql
-- Step 1: Remove all application references to the column
-- Step 2: Deploy application without the column reference
-- Step 3: Drop column in next migration
ALTER TABLE orders DROP COLUMN legacy_status;
-- For Django: use SeparateDatabaseAndState to remove from model
-- without generating DROP COLUMN (then drop in next migration)
```
### Large Data Migrations
```sql
-- BAD: Updates all rows in one transaction (locks table)
UPDATE users SET normalized_email = LOWER(email);
-- GOOD: Batch update with progress
DO $$
DECLARE
batch_size INT := 10000;
rows_updated INT;
BEGIN
LOOP
UPDATE users
SET normalized_email = LOWER(email)
WHERE id IN (
SELECT id FROM users
WHERE normalized_email IS NULL
LIMIT batch_size
FOR UPDATE SKIP LOCKED
);
GET DIAGNOSTICS rows_updated = ROW_COUNT;
RAISE NOTICE 'Updated % rows', rows_updated;
EXIT WHEN rows_updated = 0;
COMMIT;
END LOOP;
END $$;
```
## Prisma (TypeScript/Node.js)
### Workflow
```bash
# Create migration from schema changes
npx prisma migrate dev --name add_user_avatar
# Apply pending migrations in production
npx prisma migrate deploy
# Reset database (dev only)
npx prisma migrate reset
# Generate client after schema changes
npx prisma generate
```
### Schema Example
```prisma
model User {
id String @id @default(cuid())
email String @unique
name String?
avatarUrl String? @map("avatar_url")
createdAt DateTime @default(now()) @map("created_at")
updatedAt DateTime @updatedAt @map("updated_at")
orders Order[]
@@map("users")
@@index([email])
}
```
### Custom SQL Migration
For operations Prisma cannot express (concurrent indexes, data backfills):
```bash
# Create empty migration, then edit the SQL manually
npx prisma migrate dev --create-only --name add_email_index
```
```sql
-- migrations/20240115_add_email_index/migration.sql
-- Prisma cannot generate CONCURRENTLY, so we write it manually
CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_users_email ON users (email);
```
## Drizzle (TypeScript/Node.js)
### Workflow
```bash
# Generate migration from schema changes
npx drizzle-kit generate
# Apply migrations
npx drizzle-kit migrate
# Push schema directly (dev only, no migration file)
npx drizzle-kit push
```
### Schema Example
```typescript
import { pgTable, text, timestamp, uuid, boolean } from "drizzle-orm/pg-core";
export const users = pgTable("users", {
id: uuid("id").primaryKey().defaultRandom(),
email: text("email").notNull().unique(),
name: text("name"),
isActive: boolean("is_active").notNull().default(true),
createdAt: timestamp("created_at").notNull().defaultNow(),
updatedAt: timestamp("updated_at").notNull().defaultNow(),
});
```
## Django (Python)
### Workflow
```bash
# Generate migration from model changes
python manage.py makemigrations
# Apply migrations
python manage.py migrate
# Show migration status
python manage.py showmigrations
# Generate empty migration for custom SQL
python manage.py makemigrations --empty app_name -n description
```
### Data Migration
```python
from django.db import migrations
def backfill_display_names(apps, schema_editor):
User = apps.get_model("accounts", "User")
batch_size = 5000
users = User.objects.filter(display_name="")
while users.exists():
batch = list(users[:batch_size])
for user in batch:
user.display_name = user.username
User.objects.bulk_update(batch, ["display_name"], batch_size=batch_size)
def reverse_backfill(apps, schema_editor):
pass # Data migration, no reverse needed
class Migration(migrations.Migration):
dependencies = [("accounts", "0015_add_display_name")]
operations = [
migrations.RunPython(backfill_display_names, reverse_backfill),
]
```
### SeparateDatabaseAndState
Remove a column from the Django model without dropping it from the database immediately:
```python
class Migration(migrations.Migration):
operations = [
migrations.SeparateDatabaseAndState(
state_operations=[
migrations.RemoveField(model_name="user", name="legacy_field"),
],
database_operations=[], # Don't touch the DB yet
),
]
```
## golang-migrate (Go)
### Workflow
```bash
# Create migration pair
migrate create -ext sql -dir migrations -seq add_user_avatar
# Apply all pending migrations
migrate -path migrations -database "$DATABASE_URL" up
# Rollback last migration
migrate -path migrations -database "$DATABASE_URL" down 1
# Force version (fix dirty state)
migrate -path migrations -database "$DATABASE_URL" force VERSION
```
### Migration Files
```sql
-- migrations/000003_add_user_avatar.up.sql
ALTER TABLE users ADD COLUMN avatar_url TEXT;
CREATE INDEX CONCURRENTLY idx_users_avatar ON users (avatar_url) WHERE avatar_url IS NOT NULL;
-- migrations/000003_add_user_avatar.down.sql
DROP INDEX IF EXISTS idx_users_avatar;
ALTER TABLE users DROP COLUMN IF EXISTS avatar_url;
```
## Zero-Downtime Migration Strategy
For critical production changes, follow the expand-contract pattern:
```
Phase 1: EXPAND
- Add new column/table (nullable or with default)
- Deploy: app writes to BOTH old and new
- Backfill existing data
Phase 2: MIGRATE
- Deploy: app reads from NEW, writes to BOTH
- Verify data consistency
Phase 3: CONTRACT
- Deploy: app only uses NEW
- Drop old column/table in separate migration
```
### Timeline Example
```
Day 1: Migration adds new_status column (nullable)
Day 1: Deploy app v2 — writes to both status and new_status
Day 2: Run backfill migration for existing rows
Day 3: Deploy app v3 — reads from new_status only
Day 7: Migration drops old status column
```
## Anti-Patterns
| Anti-Pattern | Why It Fails | Better Approach |
|-------------|-------------|-----------------|
| Manual SQL in production | No audit trail, unrepeatable | Always use migration files |
| Editing deployed migrations | Causes drift between environments | Create new migration instead |
| NOT NULL without default | Locks table, rewrites all rows | Add nullable, backfill, then add constraint |
| Inline index on large table | Blocks writes during build | CREATE INDEX CONCURRENTLY |
| Schema + data in one migration | Hard to rollback, long transactions | Separate migrations |
| Dropping column before removing code | Application errors on missing column | Remove code first, drop column next deploy |
## When to Use This Skill
- Planning database schema changes
- Implementing zero-downtime migrations
- Setting up migration tooling
- Troubleshooting migration issues
- Reviewing migration pull requests

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---
name: deployment-patterns
description: >
Deployment workflows, CI/CD pipeline patterns, Docker containerization, health
checks, rollback strategies, and production readiness checklists for web
applications. Use when setting up deployment infrastructure or planning releases.
metadata:
origin: ECC
---
# Deployment Patterns
Production deployment workflows and CI/CD best practices.
## When to Activate
- Setting up CI/CD pipelines
- Dockerizing an application
- Planning deployment strategy (blue-green, canary, rolling)
- Implementing health checks and readiness probes
- Preparing for a production release
- Configuring environment-specific settings
## Deployment Strategies
### Rolling Deployment (Default)
Replace instances gradually — old and new versions run simultaneously during rollout.
```
Instance 1: v1 → v2 (update first)
Instance 2: v1 (still running v1)
Instance 3: v1 (still running v1)
Instance 1: v2
Instance 2: v1 → v2 (update second)
Instance 3: v1
Instance 1: v2
Instance 2: v2
Instance 3: v1 → v2 (update last)
```
**Pros:** Zero downtime, gradual rollout
**Cons:** Two versions run simultaneously — requires backward-compatible changes
**Use when:** Standard deployments, backward-compatible changes
### Blue-Green Deployment
Run two identical environments. Switch traffic atomically.
```
Blue (v1) ← traffic
Green (v2) idle, running new version
# After verification:
Blue (v1) idle (becomes standby)
Green (v2) ← traffic
```
**Pros:** Instant rollback (switch back to blue), clean cutover
**Cons:** Requires 2x infrastructure during deployment
**Use when:** Critical services, zero-tolerance for issues
### Canary Deployment
Route a small percentage of traffic to the new version first.
```
v1: 95% of traffic
v2: 5% of traffic (canary)
# If metrics look good:
v1: 50% of traffic
v2: 50% of traffic
# Final:
v2: 100% of traffic
```
**Pros:** Catches issues with real traffic before full rollout
**Cons:** Requires traffic splitting infrastructure, monitoring
**Use when:** High-traffic services, risky changes, feature flags
## Docker
### Multi-Stage Dockerfile (Node.js)
```dockerfile
# Stage 1: Install dependencies
FROM node:22-alpine AS deps
WORKDIR /app
COPY package.json package-lock.json ./
RUN npm ci --production=false
# Stage 2: Build
FROM node:22-alpine AS builder
WORKDIR /app
COPY --from=deps /app/node_modules ./node_modules
COPY . .
RUN npm run build
RUN npm prune --production
# Stage 3: Production image
FROM node:22-alpine AS runner
WORKDIR /app
RUN addgroup -g 1001 -S appgroup && adduser -S appuser -u 1001
USER appuser
COPY --from=builder --chown=appuser:appgroup /app/node_modules ./node_modules
COPY --from=builder --chown=appuser:appgroup /app/dist ./dist
COPY --from=builder --chown=appuser:appgroup /app/package.json ./
ENV NODE_ENV=production
EXPOSE 3000
HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
CMD wget --no-verbose --tries=1 --spider http://localhost:3000/health || exit 1
CMD ["node", "dist/server.js"]
```
### Multi-Stage Dockerfile (Go)
```dockerfile
FROM golang:1.22-alpine AS builder
WORKDIR /app
COPY go.mod go.sum ./
RUN go mod download
COPY . .
RUN CGO_ENABLED=0 GOOS=linux go build -ldflags="-s -w" -o /server ./cmd/server
FROM alpine:3.19 AS runner
RUN apk --no-cache add ca-certificates
RUN adduser -D -u 1001 appuser
USER appuser
COPY --from=builder /server /server
EXPOSE 8080
HEALTHCHECK --interval=30s --timeout=3s CMD wget -qO- http://localhost:8080/health || exit 1
CMD ["/server"]
```
### Multi-Stage Dockerfile (Python/Django)
```dockerfile
FROM python:3.12-slim AS builder
WORKDIR /app
RUN pip install --no-cache-dir uv
COPY requirements.txt .
RUN uv pip install --system --no-cache -r requirements.txt
FROM python:3.12-slim AS runner
WORKDIR /app
RUN useradd -r -u 1001 appuser
USER appuser
COPY --from=builder /usr/local/lib/python3.12/site-packages /usr/local/lib/python3.12/site-packages
COPY --from=builder /usr/local/bin /usr/local/bin
COPY . .
ENV PYTHONUNBUFFERED=1
EXPOSE 8000
HEALTHCHECK --interval=30s --timeout=3s CMD python -c "import urllib.request; urllib.request.urlopen('http://localhost:8000/health/')" || exit 1
CMD ["gunicorn", "config.wsgi:application", "--bind", "0.0.0.0:8000", "--workers", "4"]
```
### Docker Best Practices
```
# GOOD practices
- Use specific version tags (node:22-alpine, not node:latest)
- Multi-stage builds to minimize image size
- Run as non-root user
- Copy dependency files first (layer caching)
- Use .dockerignore to exclude node_modules, .git, tests
- Add HEALTHCHECK instruction
- Set resource limits in docker-compose or k8s
# BAD practices
- Running as root
- Using :latest tags
- Copying entire repo in one COPY layer
- Installing dev dependencies in production image
- Storing secrets in image (use env vars or secrets manager)
```
## CI/CD Pipeline
### GitHub Actions (Standard Pipeline)
```yaml
name: CI/CD
on:
push:
branches: [main]
pull_request:
branches: [main]
jobs:
test:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v4
- uses: actions/setup-node@v4
with:
node-version: 22
cache: npm
- run: npm ci
- run: npm run lint
- run: npm run typecheck
- run: npm test -- --coverage
- uses: actions/upload-artifact@v4
if: always()
with:
name: coverage
path: coverage/
build:
needs: test
runs-on: ubuntu-latest
if: github.ref == 'refs/heads/main'
steps:
- uses: actions/checkout@v4
- uses: docker/setup-buildx-action@v3
- uses: docker/login-action@v3
with:
registry: ghcr.io
username: ${{ github.actor }}
password: ${{ secrets.GITHUB_TOKEN }}
- uses: docker/build-push-action@v5
with:
push: true
tags: ghcr.io/${{ github.repository }}:${{ github.sha }}
cache-from: type=gha
cache-to: type=gha,mode=max
deploy:
needs: build
runs-on: ubuntu-latest
if: github.ref == 'refs/heads/main'
environment: production
steps:
- name: Deploy to production
run: |
# Platform-specific deployment command
# Railway: railway up
# Vercel: vercel --prod
# K8s: kubectl set image deployment/app app=ghcr.io/${{ github.repository }}:${{ github.sha }}
echo "Deploying ${{ github.sha }}"
```
### Pipeline Stages
```
PR opened:
lint → typecheck → unit tests → integration tests → preview deploy
Merged to main:
lint → typecheck → unit tests → integration tests → build image → deploy staging → smoke tests → deploy production
```
## Health Checks
### Health Check Endpoint
```typescript
// Simple health check
app.get("/health", (req, res) => {
res.status(200).json({ status: "ok" });
});
// Detailed health check (for internal monitoring)
app.get("/health/detailed", async (req, res) => {
const checks = {
database: await checkDatabase(),
redis: await checkRedis(),
externalApi: await checkExternalApi(),
};
const allHealthy = Object.values(checks).every(c => c.status === "ok");
res.status(allHealthy ? 200 : 503).json({
status: allHealthy ? "ok" : "degraded",
timestamp: new Date().toISOString(),
version: process.env.APP_VERSION || "unknown",
uptime: process.uptime(),
checks,
});
});
async function checkDatabase(): Promise<HealthCheck> {
try {
await db.query("SELECT 1");
return { status: "ok", latency_ms: 2 };
} catch (err) {
return { status: "error", message: "Database unreachable" };
}
}
```
### Kubernetes Probes
```yaml
livenessProbe:
httpGet:
path: /health
port: 3000
initialDelaySeconds: 10
periodSeconds: 30
failureThreshold: 3
readinessProbe:
httpGet:
path: /health
port: 3000
initialDelaySeconds: 5
periodSeconds: 10
failureThreshold: 2
startupProbe:
httpGet:
path: /health
port: 3000
initialDelaySeconds: 0
periodSeconds: 5
failureThreshold: 30 # 30 * 5s = 150s max startup time
```
## Environment Configuration
### Twelve-Factor App Pattern
```bash
# All config via environment variables — never in code
DATABASE_URL=postgres://user:pass@host:5432/db
REDIS_URL=redis://host:6379/0
API_KEY=${API_KEY} # injected by secrets manager
LOG_LEVEL=info
PORT=3000
# Environment-specific behavior
NODE_ENV=production # or staging, development
APP_ENV=production # explicit app environment
```
### Configuration Validation
```typescript
import { z } from "zod";
const envSchema = z.object({
NODE_ENV: z.enum(["development", "staging", "production"]),
PORT: z.coerce.number().default(3000),
DATABASE_URL: z.string().url(),
REDIS_URL: z.string().url(),
JWT_SECRET: z.string().min(32),
LOG_LEVEL: z.enum(["debug", "info", "warn", "error"]).default("info"),
});
// Validate at startup — fail fast if config is wrong
export const env = envSchema.parse(process.env);
```
## Rollback Strategy
### Instant Rollback
```bash
# Docker/Kubernetes: point to previous image
kubectl rollout undo deployment/app
# Vercel: promote previous deployment
vercel rollback
# Railway: redeploy previous commit
railway up --commit <previous-sha>
# Database: rollback migration (if reversible)
npx prisma migrate resolve --rolled-back <migration-name>
```
### Rollback Checklist
- [ ] Previous image/artifact is available and tagged
- [ ] Database migrations are backward-compatible (no destructive changes)
- [ ] Feature flags can disable new features without deploy
- [ ] Monitoring alerts configured for error rate spikes
- [ ] Rollback tested in staging before production release
## Production Readiness Checklist
Before any production deployment:
### Application
- [ ] All tests pass (unit, integration, E2E)
- [ ] No hardcoded secrets in code or config files
- [ ] Error handling covers all edge cases
- [ ] Logging is structured (JSON) and does not contain PII
- [ ] Health check endpoint returns meaningful status
### Infrastructure
- [ ] Docker image builds reproducibly (pinned versions)
- [ ] Environment variables documented and validated at startup
- [ ] Resource limits set (CPU, memory)
- [ ] Horizontal scaling configured (min/max instances)
- [ ] SSL/TLS enabled on all endpoints
### Monitoring
- [ ] Application metrics exported (request rate, latency, errors)
- [ ] Alerts configured for error rate > threshold
- [ ] Log aggregation set up (structured logs, searchable)
- [ ] Uptime monitoring on health endpoint
### Security
- [ ] Dependencies scanned for CVEs
- [ ] CORS configured for allowed origins only
- [ ] Rate limiting enabled on public endpoints
- [ ] Authentication and authorization verified
- [ ] Security headers set (CSP, HSTS, X-Frame-Options)
### Operations
- [ ] Rollback plan documented and tested
- [ ] Database migration tested against production-sized data
- [ ] Runbook for common failure scenarios
- [ ] On-call rotation and escalation path defined
## When to Use This Skill
- Setting up CI/CD pipelines
- Dockerizing applications
- Planning deployment strategies
- Implementing health checks
- Preparing for production releases
- Troubleshooting deployment issues

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---
name: docker-patterns
description: >
Docker and Docker Compose patterns for local development, container security,
networking, volume strategies, and multi-service orchestration. Use when
setting up containerized development environments or reviewing Docker configurations.
metadata:
origin: ECC
---
# Docker Patterns
Docker and Docker Compose best practices for containerized development.
## When to Activate
- Setting up Docker Compose for local development
- Designing multi-container architectures
- Troubleshooting container networking or volume issues
- Reviewing Dockerfiles for security and size
- Migrating from local dev to containerized workflow
## Docker Compose for Local Development
### Standard Web App Stack
```yaml
# docker-compose.yml
services:
app:
build:
context: .
target: dev # Use dev stage of multi-stage Dockerfile
ports:
- "3000:3000"
volumes:
- .:/app # Bind mount for hot reload
- /app/node_modules # Anonymous volume -- preserves container deps
environment:
- DATABASE_URL=postgres://postgres:postgres@db:5432/app_dev
- REDIS_URL=redis://redis:6379/0
- NODE_ENV=development
depends_on:
db:
condition: service_healthy
redis:
condition: service_started
command: npm run dev
db:
image: postgres:16-alpine
ports:
- "5432:5432"
environment:
POSTGRES_USER: postgres
POSTGRES_PASSWORD: postgres
POSTGRES_DB: app_dev
volumes:
- pgdata:/var/lib/postgresql/data
- ./scripts/init-db.sql:/docker-entrypoint-initdb.d/init.sql
healthcheck:
test: ["CMD-SHELL", "pg_isready -U postgres"]
interval: 5s
timeout: 3s
retries: 5
redis:
image: redis:7-alpine
ports:
- "6379:6379"
volumes:
- redisdata:/data
mailpit: # Local email testing
image: axllent/mailpit
ports:
- "8025:8025" # Web UI
- "1025:1025" # SMTP
volumes:
pgdata:
redisdata:
```
### Development vs Production Dockerfile
```dockerfile
# Stage: dependencies
FROM node:22-alpine AS deps
WORKDIR /app
COPY package.json package-lock.json ./
RUN npm ci
# Stage: dev (hot reload, debug tools)
FROM node:22-alpine AS dev
WORKDIR /app
COPY --from=deps /app/node_modules ./node_modules
COPY . .
EXPOSE 3000
CMD ["npm", "run", "dev"]
# Stage: build
FROM node:22-alpine AS build
WORKDIR /app
COPY --from=deps /app/node_modules ./node_modules
COPY . .
RUN npm run build && npm prune --production
# Stage: production (minimal image)
FROM node:22-alpine AS production
WORKDIR /app
RUN addgroup -g 1001 -S appgroup && adduser -S appuser -u 1001
USER appuser
COPY --from=build --chown=appuser:appgroup /app/dist ./dist
COPY --from=build --chown=appuser:appgroup /app/node_modules ./node_modules
COPY --from=build --chown=appuser:appgroup /app/package.json ./
ENV NODE_ENV=production
EXPOSE 3000
HEALTHCHECK --interval=30s --timeout=3s CMD wget -qO- http://localhost:3000/health || exit 1
CMD ["node", "dist/server.js"]
```
### Override Files
```yaml
# docker-compose.override.yml (auto-loaded, dev-only settings)
services:
app:
environment:
- DEBUG=app:*
- LOG_LEVEL=debug
ports:
- "9229:9229" # Node.js debugger
# docker-compose.prod.yml (explicit for production)
services:
app:
build:
target: production
restart: always
deploy:
resources:
limits:
cpus: "1.0"
memory: 512M
```
```bash
# Development (auto-loads override)
docker compose up
# Production
docker compose -f docker-compose.yml -f docker-compose.prod.yml up -d
```
## Networking
### Service Discovery
Services in the same Compose network resolve by service name:
```
# From "app" container:
postgres://postgres:postgres@db:5432/app_dev # "db" resolves to the db container
redis://redis:6379/0 # "redis" resolves to the redis container
```
### Custom Networks
```yaml
services:
frontend:
networks:
- frontend-net
api:
networks:
- frontend-net
- backend-net
db:
networks:
- backend-net # Only reachable from api, not frontend
networks:
frontend-net:
backend-net:
```
### Exposing Only What's Needed
```yaml
services:
db:
ports:
- "127.0.0.1:5432:5432" # Only accessible from host, not network
# Omit ports entirely in production -- accessible only within Docker network
```
## Volume Strategies
```yaml
volumes:
# Named volume: persists across container restarts, managed by Docker
pgdata:
# Bind mount: maps host directory into container (for development)
# - ./src:/app/src
# Anonymous volume: preserves container-generated content from bind mount override
# - /app/node_modules
```
### Common Patterns
```yaml
services:
app:
volumes:
- .:/app # Source code (bind mount for hot reload)
- /app/node_modules # Protect container's node_modules from host
- /app/.next # Protect build cache
db:
volumes:
- pgdata:/var/lib/postgresql/data # Persistent data
- ./scripts/init.sql:/docker-entrypoint-initdb.d/init.sql # Init scripts
```
## Container Security
### Dockerfile Hardening
```dockerfile
# 1. Use specific tags (never :latest)
FROM node:22.12-alpine3.20
# 2. Run as non-root
RUN addgroup -g 1001 -S app && adduser -S app -u 1001
USER app
# 3. Drop capabilities (in compose)
# 4. Read-only root filesystem where possible
# 5. No secrets in image layers
```
### Compose Security
```yaml
services:
app:
security_opt:
- no-new-privileges:true
read_only: true
tmpfs:
- /tmp
- /app/.cache
cap_drop:
- ALL
cap_add:
- NET_BIND_SERVICE # Only if binding to ports < 1024
```
### Secret Management
```yaml
# GOOD: Use environment variables (injected at runtime)
services:
app:
env_file:
- .env # Never commit .env to git
environment:
- API_KEY # Inherits from host environment
# GOOD: Docker secrets (Swarm mode)
secrets:
db_password:
file: ./secrets/db_password.txt
services:
db:
secrets:
- db_password
# BAD: Hardcoded in image
# ENV API_KEY=sk-proj-xxxxx # NEVER DO THIS
```
## .dockerignore
```
node_modules
.git
.env
.env.*
dist
coverage
*.log
.next
.cache
docker-compose*.yml
Dockerfile*
README.md
tests/
```
## Debugging
### Common Commands
```bash
# View logs
docker compose logs -f app # Follow app logs
docker compose logs --tail=50 db # Last 50 lines from db
# Execute commands in running container
docker compose exec app sh # Shell into app
docker compose exec db psql -U postgres # Connect to postgres
# Inspect
docker compose ps # Running services
docker compose top # Processes in each container
docker stats # Resource usage
# Rebuild
docker compose up --build # Rebuild images
docker compose build --no-cache app # Force full rebuild
# Clean up
docker compose down # Stop and remove containers
docker compose down -v # Also remove volumes (DESTRUCTIVE)
docker system prune # Remove unused images/containers
```
### Debugging Network Issues
```bash
# Check DNS resolution inside container
docker compose exec app nslookup db
# Check connectivity
docker compose exec app wget -qO- http://api:3000/health
# Inspect network
docker network ls
docker network inspect <project>_default
```
## Anti-Patterns
```
# BAD: Using docker compose in production without orchestration
# Use Kubernetes, ECS, or Docker Swarm for production multi-container workloads
# BAD: Storing data in containers without volumes
# Containers are ephemeral -- all data lost on restart without volumes
# BAD: Running as root
# Always create and use a non-root user
# BAD: Using :latest tag
# Pin to specific versions for reproducible builds
# BAD: One giant container with all services
# Separate concerns: one process per container
# BAD: Putting secrets in docker-compose.yml
# Use .env files (gitignored) or Docker secrets
```
## When to Use This Skill
- Setting up Docker Compose for local development
- Designing multi-container architectures
- Troubleshooting container issues
- Reviewing Dockerfiles for security
- Implementing container best practices

View File

@@ -0,0 +1,328 @@
---
name: e2e-testing
description: >
Playwright E2E testing patterns, Page Object Model, configuration, CI/CD integration, artifact management, and flaky test strategies.
metadata:
origin: ECC
---
# E2E Testing Patterns
Comprehensive Playwright patterns for building stable, fast, and maintainable E2E test suites.
## Test File Organization
```
tests/
├── e2e/
│ ├── auth/
│ │ ├── login.spec.ts
│ │ ├── logout.spec.ts
│ │ └── register.spec.ts
│ ├── features/
│ │ ├── browse.spec.ts
│ │ ├── search.spec.ts
│ │ └── create.spec.ts
│ └── api/
│ └── endpoints.spec.ts
├── fixtures/
│ ├── auth.ts
│ └── data.ts
└── playwright.config.ts
```
## Page Object Model (POM)
```typescript
import { Page, Locator } from '@playwright/test'
export class ItemsPage {
readonly page: Page
readonly searchInput: Locator
readonly itemCards: Locator
readonly createButton: Locator
constructor(page: Page) {
this.page = page
this.searchInput = page.locator('[data-testid="search-input"]')
this.itemCards = page.locator('[data-testid="item-card"]')
this.createButton = page.locator('[data-testid="create-btn"]')
}
async goto() {
await this.page.goto('/items')
await this.page.waitForLoadState('networkidle')
}
async search(query: string) {
await this.searchInput.fill(query)
await this.page.waitForResponse(resp => resp.url().includes('/api/search'))
await this.page.waitForLoadState('networkidle')
}
async getItemCount() {
return await this.itemCards.count()
}
}
```
## Test Structure
```typescript
import { test, expect } from '@playwright/test'
import { ItemsPage } from '../../pages/ItemsPage'
test.describe('Item Search', () => {
let itemsPage: ItemsPage
test.beforeEach(async ({ page }) => {
itemsPage = new ItemsPage(page)
await itemsPage.goto()
})
test('should search by keyword', async ({ page }) => {
await itemsPage.search('test')
const count = await itemsPage.getItemCount()
expect(count).toBeGreaterThan(0)
await expect(itemsPage.itemCards.first()).toContainText(/test/i)
await page.screenshot({ path: 'artifacts/search-results.png' })
})
test('should handle no results', async ({ page }) => {
await itemsPage.search('xyznonexistent123')
await expect(page.locator('[data-testid="no-results"]')).toBeVisible()
expect(await itemsPage.getItemCount()).toBe(0)
})
})
```
## Playwright Configuration
```typescript
import { defineConfig, devices } from '@playwright/test'
export default defineConfig({
testDir: './tests/e2e',
fullyParallel: true,
forbidOnly: !!process.env.CI,
retries: process.env.CI ? 2 : 0,
workers: process.env.CI ? 1 : undefined,
reporter: [
['html', { outputFolder: 'playwright-report' }],
['junit', { outputFile: 'playwright-results.xml' }],
['json', { outputFile: 'playwright-results.json' }]
],
use: {
baseURL: process.env.BASE_URL || 'http://localhost:3000',
trace: 'on-first-retry',
screenshot: 'only-on-failure',
video: 'retain-on-failure',
actionTimeout: 10000,
navigationTimeout: 30000,
},
projects: [
{ name: 'chromium', use: { ...devices['Desktop Chrome'] } },
{ name: 'firefox', use: { ...devices['Desktop Firefox'] } },
{ name: 'webkit', use: { ...devices['Desktop Safari'] } },
{ name: 'mobile-chrome', use: { ...devices['Pixel 5'] } },
],
webServer: {
command: 'npm run dev',
url: 'http://localhost:3000',
reuseExistingServer: !process.env.CI,
timeout: 120000,
},
})
```
## Flaky Test Patterns
### Quarantine
```typescript
test('flaky: complex search', async ({ page }) => {
test.fixme(true, 'Flaky - Issue #123')
// test code...
})
test('conditional skip', async ({ page }) => {
test.skip(process.env.CI, 'Flaky in CI - Issue #123')
// test code...
})
```
### Identify Flakiness
```bash
npx playwright test tests/search.spec.ts --repeat-each=10
npx playwright test tests/search.spec.ts --retries=3
```
### Common Causes & Fixes
**Race conditions:**
```typescript
// Bad: assumes element is ready
await page.click('[data-testid="button"]')
// Good: auto-wait locator
await page.locator('[data-testid="button"]').click()
```
**Network timing:**
```typescript
// Bad: arbitrary timeout
await page.waitForTimeout(5000)
// Good: wait for specific condition
await page.waitForResponse(resp => resp.url().includes('/api/data'))
```
**Animation timing:**
```typescript
// Bad: click during animation
await page.click('[data-testid="menu-item"]')
// Good: wait for stability
await page.locator('[data-testid="menu-item"]').waitFor({ state: 'visible' })
await page.waitForLoadState('networkidle')
await page.locator('[data-testid="menu-item"]').click()
```
## Artifact Management
### Screenshots
```typescript
await page.screenshot({ path: 'artifacts/after-login.png' })
await page.screenshot({ path: 'artifacts/full-page.png', fullPage: true })
await page.locator('[data-testid="chart"]').screenshot({ path: 'artifacts/chart.png' })
```
### Traces
```typescript
await browser.startTracing(page, {
path: 'artifacts/trace.json',
screenshots: true,
snapshots: true,
})
// ... test actions ...
await browser.stopTracing()
```
### Video
```typescript
// In playwright.config.ts
use: {
video: 'retain-on-failure',
videosPath: 'artifacts/videos/'
}
```
## CI/CD Integration
```yaml
# .github/workflows/e2e.yml
name: E2E Tests
on: [push, pull_request]
jobs:
test:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v4
- uses: actions/setup-node@v4
with:
node-version: 20
- run: npm ci
- run: npx playwright install --with-deps
- run: npx playwright test
env:
BASE_URL: ${{ vars.STAGING_URL }}
- uses: actions/upload-artifact@v4
if: always()
with:
name: playwright-report
path: playwright-report/
retention-days: 30
```
## Test Report Template
```markdown
# E2E Test Report
**Date:** YYYY-MM-DD HH:MM
**Duration:** Xm Ys
**Status:** PASSING / FAILING
## Summary
- Total: X | Passed: Y (Z%) | Failed: A | Flaky: B | Skipped: C
## Failed Tests
### test-name
**File:** `tests/e2e/feature.spec.ts:45`
**Error:** Expected element to be visible
**Screenshot:** artifacts/failed.png
**Recommended Fix:** [description]
## Artifacts
- HTML Report: playwright-report/index.html
- Screenshots: artifacts/*.png
- Videos: artifacts/videos/*.webm
- Traces: artifacts/*.zip
```
## Wallet / Web3 Testing
```typescript
test('wallet connection', async ({ page, context }) => {
// Mock wallet provider
await context.addInitScript(() => {
window.ethereum = {
isMetaMask: true,
request: async ({ method }) => {
if (method === 'eth_requestAccounts')
return ['0x1234567890123456789012345678901234567890']
if (method === 'eth_chainId') return '0x1'
}
}
})
await page.goto('/')
await page.locator('[data-testid="connect-wallet"]').click()
await expect(page.locator('[data-testid="wallet-address"]')).toContainText('0x1234')
})
```
## Financial / Critical Flow Testing
```typescript
test('trade execution', async ({ page }) => {
// Skip on production — real money
test.skip(process.env.NODE_ENV === 'production', 'Skip on production')
await page.goto('/markets/test-market')
await page.locator('[data-testid="position-yes"]').click()
await page.locator('[data-testid="trade-amount"]').fill('1.0')
// Verify preview
const preview = page.locator('[data-testid="trade-preview"]')
await expect(preview).toContainText('1.0')
// Confirm and wait for blockchain
await page.locator('[data-testid="confirm-trade"]').click()
await page.waitForResponse(
resp => resp.url().includes('/api/trade') && resp.status() === 200,
{ timeout: 30000 }
)
await expect(page.locator('[data-testid="trade-success"]')).toBeVisible()
})
```

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---
name: frontend-patterns
description: >
Frontend development patterns for React, Next.js, state management, performance optimization, and UI best practices.
metadata:
origin: ECC
---
# Frontend Development Patterns
Modern frontend patterns for React, Next.js, and performant user interfaces.
## When to Activate
- Building React components (composition, props, rendering)
- Managing state (useState, useReducer, Zustand, Context)
- Implementing data fetching (SWR, React Query, server components)
- Optimizing performance (memoization, virtualization, code splitting)
- Working with forms (validation, controlled inputs, Zod schemas)
- Handling client-side routing and navigation
- Building accessible, responsive UI patterns
## Component Patterns
### Composition Over Inheritance
```typescript
// ✅ GOOD: Component composition
interface CardProps {
children: React.ReactNode
variant?: 'default' | 'outlined'
}
export function Card({ children, variant = 'default' }: CardProps) {
return <div className={`card card-${variant}`}>{children}</div>
}
export function CardHeader({ children }: { children: React.ReactNode }) {
return <div className="card-header">{children}</div>
}
export function CardBody({ children }: { children: React.ReactNode }) {
return <div className="card-body">{children}</div>
}
// Usage
<Card>
<CardHeader>Title</CardHeader>
<CardBody>Content</CardBody>
</Card>
```
### Compound Components
```typescript
interface TabsContextValue {
activeTab: string
setActiveTab: (tab: string) => void
}
const TabsContext = createContext<TabsContextValue | undefined>(undefined)
export function Tabs({ children, defaultTab }: {
children: React.ReactNode
defaultTab: string
}) {
const [activeTab, setActiveTab] = useState(defaultTab)
return (
<TabsContext.Provider value={{ activeTab, setActiveTab }}>
{children}
</TabsContext.Provider>
)
}
export function TabList({ children }: { children: React.ReactNode }) {
return <div className="tab-list">{children}</div>
}
export function Tab({ id, children }: { id: string, children: React.ReactNode }) {
const context = useContext(TabsContext)
if (!context) throw new Error('Tab must be used within Tabs')
return (
<button
className={context.activeTab === id ? 'active' : ''}
onClick={() => context.setActiveTab(id)}
>
{children}
</button>
)
}
// Usage
<Tabs defaultTab="overview">
<TabList>
<Tab id="overview">Overview</Tab>
<Tab id="details">Details</Tab>
</TabList>
</Tabs>
```
### Render Props Pattern
```typescript
interface DataLoaderProps<T> {
url: string
children: (data: T | null, loading: boolean, error: Error | null) => React.ReactNode
}
export function DataLoader<T>({ url, children }: DataLoaderProps<T>) {
const [data, setData] = useState<T | null>(null)
const [loading, setLoading] = useState(true)
const [error, setError] = useState<Error | null>(null)
useEffect(() => {
fetch(url)
.then(res => res.json())
.then(setData)
.catch(setError)
.finally(() => setLoading(false))
}, [url])
return <>{children(data, loading, error)}</>
}
// Usage
<DataLoader<Market[]> url="/api/markets">
{(markets, loading, error) => {
if (loading) return <Spinner />
if (error) return <Error error={error} />
return <MarketList markets={markets!} />
}}
</DataLoader>
```
## Custom Hooks Patterns
### State Management Hook
```typescript
export function useToggle(initialValue = false): [boolean, () => void] {
const [value, setValue] = useState(initialValue)
const toggle = useCallback(() => {
setValue(v => !v)
}, [])
return [value, toggle]
}
// Usage
const [isOpen, toggleOpen] = useToggle()
```
### Async Data Fetching Hook
```typescript
interface UseQueryOptions<T> {
onSuccess?: (data: T) => void
onError?: (error: Error) => void
enabled?: boolean
}
export function useQuery<T>(
key: string,
fetcher: () => Promise<T>,
options?: UseQueryOptions<T>
) {
const [data, setData] = useState<T | null>(null)
const [error, setError] = useState<Error | null>(null)
const [loading, setLoading] = useState(false)
const refetch = useCallback(async () => {
setLoading(true)
setError(null)
try {
const result = await fetcher()
setData(result)
options?.onSuccess?.(result)
} catch (err) {
const error = err as Error
setError(error)
options?.onError?.(error)
} finally {
setLoading(false)
}
}, [fetcher, options])
useEffect(() => {
if (options?.enabled !== false) {
refetch()
}
}, [key, refetch, options?.enabled])
return { data, error, loading, refetch }
}
// Usage
const { data: markets, loading, error, refetch } = useQuery(
'markets',
() => fetch('/api/markets').then(r => r.json()),
{
onSuccess: data => console.log('Fetched', data.length, 'markets'),
onError: err => console.error('Failed:', err)
}
)
```
### Debounce Hook
```typescript
export function useDebounce<T>(value: T, delay: number): T {
const [debouncedValue, setDebouncedValue] = useState<T>(value)
useEffect(() => {
const handler = setTimeout(() => {
setDebouncedValue(value)
}, delay)
return () => clearTimeout(handler)
}, [value, delay])
return debouncedValue
}
// Usage
const [searchQuery, setSearchQuery] = useState('')
const debouncedQuery = useDebounce(searchQuery, 500)
useEffect(() => {
if (debouncedQuery) {
performSearch(debouncedQuery)
}
}, [debouncedQuery])
```
## State Management Patterns
### Context + Reducer Pattern
```typescript
interface State {
markets: Market[]
selectedMarket: Market | null
loading: boolean
}
type Action =
| { type: 'SET_MARKETS'; payload: Market[] }
| { type: 'SELECT_MARKET'; payload: Market }
| { type: 'SET_LOADING'; payload: boolean }
function reducer(state: State, action: Action): State {
switch (action.type) {
case 'SET_MARKETS':
return { ...state, markets: action.payload }
case 'SELECT_MARKET':
return { ...state, selectedMarket: action.payload }
case 'SET_LOADING':
return { ...state, loading: action.payload }
default:
return state
}
}
const MarketContext = createContext<{
state: State
dispatch: Dispatch<Action>
} | undefined>(undefined)
export function MarketProvider({ children }: { children: React.ReactNode }) {
const [state, dispatch] = useReducer(reducer, {
markets: [],
selectedMarket: null,
loading: false
})
return (
<MarketContext.Provider value={{ state, dispatch }}>
{children}
</MarketContext.Provider>
)
}
export function useMarkets() {
const context = useContext(MarketContext)
if (!context) throw new Error('useMarkets must be used within MarketProvider')
return context
}
```
## Performance Optimization
### Memoization
```typescript
// ✅ useMemo for expensive computations
const sortedMarkets = useMemo(() => {
return markets.sort((a, b) => b.volume - a.volume)
}, [markets])
// ✅ useCallback for functions passed to children
const handleSearch = useCallback((query: string) => {
setSearchQuery(query)
}, [])
// ✅ React.memo for pure components
export const MarketCard = React.memo<MarketCardProps>(({ market }) => {
return (
<div className="market-card">
<h3>{market.name}</h3>
<p>{market.description}</p>
</div>
)
})
```
### Code Splitting & Lazy Loading
```typescript
import { lazy, Suspense } from 'react'
// ✅ Lazy load heavy components
const HeavyChart = lazy(() => import('./HeavyChart'))
const ThreeJsBackground = lazy(() => import('./ThreeJsBackground'))
export function Dashboard() {
return (
<div>
<Suspense fallback={<ChartSkeleton />}>
<HeavyChart data={data} />
</Suspense>
<Suspense fallback={null}>
<ThreeJsBackground />
</Suspense>
</div>
)
}
```
### Virtualization for Long Lists
```typescript
import { useVirtualizer } from '@tanstack/react-virtual'
export function VirtualMarketList({ markets }: { markets: Market[] }) {
const parentRef = useRef<HTMLDivElement>(null)
const virtualizer = useVirtualizer({
count: markets.length,
getScrollElement: () => parentRef.current,
estimateSize: () => 100, // Estimated row height
overscan: 5 // Extra items to render
})
return (
<div ref={parentRef} style={{ height: '600px', overflow: 'auto' }}>
<div
style={{
height: `${virtualizer.getTotalSize()}px`,
position: 'relative'
}}
>
{virtualizer.getVirtualItems().map(virtualRow => (
<div
key={virtualRow.index}
style={{
position: 'absolute',
top: 0,
left: 0,
width: '100%',
height: `${virtualRow.size}px`,
transform: `translateY(${virtualRow.start}px)`
}}
>
<MarketCard market={markets[virtualRow.index]} />
</div>
))}
</div>
</div>
)
}
```
## Form Handling Patterns
### Controlled Form with Validation
```typescript
interface FormData {
name: string
description: string
endDate: string
}
interface FormErrors {
name?: string
description?: string
endDate?: string
}
export function CreateMarketForm() {
const [formData, setFormData] = useState<FormData>({
name: '',
description: '',
endDate: ''
})
const [errors, setErrors] = useState<FormErrors>({})
const validate = (): boolean => {
const newErrors: FormErrors = {}
if (!formData.name.trim()) {
newErrors.name = 'Name is required'
} else if (formData.name.length > 200) {
newErrors.name = 'Name must be under 200 characters'
}
if (!formData.description.trim()) {
newErrors.description = 'Description is required'
}
if (!formData.endDate) {
newErrors.endDate = 'End date is required'
}
setErrors(newErrors)
return Object.keys(newErrors).length === 0
}
const handleSubmit = async (e: React.FormEvent) => {
e.preventDefault()
if (!validate()) return
try {
await createMarket(formData)
// Success handling
} catch (error) {
// Error handling
}
}
return (
<form onSubmit={handleSubmit}>
<input
value={formData.name}
onChange={e => setFormData(prev => ({ ...prev, name: e.target.value }))}
placeholder="Market name"
/>
{errors.name && <span className="error">{errors.name}</span>}
{/* Other fields */}
<button type="submit">Create Market</button>
</form>
)
}
```
## Error Boundary Pattern
```typescript
interface ErrorBoundaryState {
hasError: boolean
error: Error | null
}
export class ErrorBoundary extends React.Component<
{ children: React.ReactNode },
ErrorBoundaryState
> {
state: ErrorBoundaryState = {
hasError: false,
error: null
}
static getDerivedStateFromError(error: Error): ErrorBoundaryState {
return { hasError: true, error }
}
componentDidCatch(error: Error, errorInfo: React.ErrorInfo) {
console.error('Error boundary caught:', error, errorInfo)
}
render() {
if (this.state.hasError) {
return (
<div className="error-fallback">
<h2>Something went wrong</h2>
<p>{this.state.error?.message}</p>
<button onClick={() => this.setState({ hasError: false })}>
Try again
</button>
</div>
)
}
return this.props.children
}
}
// Usage
<ErrorBoundary>
<App />
</ErrorBoundary>
```
## Animation Patterns
### Framer Motion Animations
```typescript
import { motion, AnimatePresence } from 'framer-motion'
// ✅ List animations
export function AnimatedMarketList({ markets }: { markets: Market[] }) {
return (
<AnimatePresence>
{markets.map(market => (
<motion.div
key={market.id}
initial={{ opacity: 0, y: 20 }}
animate={{ opacity: 1, y: 0 }}
exit={{ opacity: 0, y: -20 }}
transition={{ duration: 0.3 }}
>
<MarketCard market={market} />
</motion.div>
))}
</AnimatePresence>
)
}
// ✅ Modal animations
export function Modal({ isOpen, onClose, children }: ModalProps) {
return (
<AnimatePresence>
{isOpen && (
<>
<motion.div
className="modal-overlay"
initial={{ opacity: 0 }}
animate={{ opacity: 1 }}
exit={{ opacity: 0 }}
onClick={onClose}
/>
<motion.div
className="modal-content"
initial={{ opacity: 0, scale: 0.9, y: 20 }}
animate={{ opacity: 1, scale: 1, y: 0 }}
exit={{ opacity: 0, scale: 0.9, y: 20 }}
>
{children}
</motion.div>
</>
)}
</AnimatePresence>
)
}
```
## Accessibility Patterns
### Keyboard Navigation
```typescript
export function Dropdown({ options, onSelect }: DropdownProps) {
const [isOpen, setIsOpen] = useState(false)
const [activeIndex, setActiveIndex] = useState(0)
const handleKeyDown = (e: React.KeyboardEvent) => {
switch (e.key) {
case 'ArrowDown':
e.preventDefault()
setActiveIndex(i => Math.min(i + 1, options.length - 1))
break
case 'ArrowUp':
e.preventDefault()
setActiveIndex(i => Math.max(i - 1, 0))
break
case 'Enter':
e.preventDefault()
onSelect(options[activeIndex])
setIsOpen(false)
break
case 'Escape':
setIsOpen(false)
break
}
}
return (
<div
role="combobox"
aria-expanded={isOpen}
aria-haspopup="listbox"
onKeyDown={handleKeyDown}
>
{/* Dropdown implementation */}
</div>
)
}
```
### Focus Management
```typescript
export function Modal({ isOpen, onClose, children }: ModalProps) {
const modalRef = useRef<HTMLDivElement>(null)
const previousFocusRef = useRef<HTMLElement | null>(null)
useEffect(() => {
if (isOpen) {
// Save currently focused element
previousFocusRef.current = document.activeElement as HTMLElement
// Focus modal
modalRef.current?.focus()
} else {
// Restore focus when closing
previousFocusRef.current?.focus()
}
}, [isOpen])
return isOpen ? (
<div
ref={modalRef}
role="dialog"
aria-modal="true"
tabIndex={-1}
onKeyDown={e => e.key === 'Escape' && onClose()}
>
{children}
</div>
) : null
}
```
**Remember**: Modern frontend patterns enable maintainable, performant user interfaces. Choose patterns that fit your project complexity.

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---
name: golang-patterns
description: >
Go-specific design patterns and best practices including functional options,
small interfaces, dependency injection, concurrency patterns, error handling,
and package organization. Use when working with Go code to apply idiomatic
Go patterns.
metadata:
origin: ECC
globs: ["**/*.go", "**/go.mod", "**/go.sum"]
---
# Go Patterns
> This skill provides comprehensive Go patterns extending common design principles with Go-specific idioms.
## Functional Options
Use the functional options pattern for flexible constructor configuration:
```go
type Option func(*Server)
func WithPort(port int) Option {
return func(s *Server) { s.port = port }
}
func NewServer(opts ...Option) *Server {
s := &Server{port: 8080}
for _, opt := range opts {
opt(s)
}
return s
}
```
**Benefits:**
- Backward compatible API evolution
- Optional parameters with defaults
- Self-documenting configuration
## Small Interfaces
Define interfaces where they are used, not where they are implemented.
**Principle:** Accept interfaces, return structs
```go
// Good: Small, focused interface defined at point of use
type UserStore interface {
GetUser(id string) (*User, error)
}
func ProcessUser(store UserStore, id string) error {
user, err := store.GetUser(id)
// ...
}
```
**Benefits:**
- Easier testing and mocking
- Loose coupling
- Clear dependencies
## Dependency Injection
Use constructor functions to inject dependencies:
```go
func NewUserService(repo UserRepository, logger Logger) *UserService {
return &UserService{
repo: repo,
logger: logger,
}
}
```
**Pattern:**
- Constructor functions (New* prefix)
- Explicit dependencies as parameters
- Return concrete types
- Validate dependencies in constructor
## Concurrency Patterns
### Worker Pool
```go
func workerPool(jobs <-chan Job, results chan<- Result, workers int) {
var wg sync.WaitGroup
for i := 0; i < workers; i++ {
wg.Add(1)
go func() {
defer wg.Done()
for job := range jobs {
results <- processJob(job)
}
}()
}
wg.Wait()
close(results)
}
```
### Context Propagation
Always pass context as first parameter:
```go
func FetchUser(ctx context.Context, id string) (*User, error) {
// Check context cancellation
select {
case <-ctx.Done():
return nil, ctx.Err()
default:
}
// ... fetch logic
}
```
## Error Handling
### Error Wrapping
```go
if err != nil {
return fmt.Errorf("failed to fetch user %s: %w", id, err)
}
```
### Custom Errors
```go
type ValidationError struct {
Field string
Msg string
}
func (e *ValidationError) Error() string {
return fmt.Sprintf("%s: %s", e.Field, e.Msg)
}
```
### Sentinel Errors
```go
var (
ErrNotFound = errors.New("not found")
ErrInvalid = errors.New("invalid input")
)
// Check with errors.Is
if errors.Is(err, ErrNotFound) {
// handle not found
}
```
## Package Organization
### Structure
```
project/
├── cmd/ # Main applications
│ └── server/
│ └── main.go
├── internal/ # Private application code
│ ├── domain/ # Business logic
│ ├── handler/ # HTTP handlers
│ └── repository/ # Data access
└── pkg/ # Public libraries
```
### Naming Conventions
- Package names: lowercase, single word
- Avoid stutter: `user.User` not `user.UserModel`
- Use `internal/` for private code
- Keep `main` package minimal
## Testing Patterns
### Table-Driven Tests
```go
func TestValidate(t *testing.T) {
tests := []struct {
name string
input string
wantErr bool
}{
{"valid", "test@example.com", false},
{"invalid", "not-an-email", true},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
err := Validate(tt.input)
if (err != nil) != tt.wantErr {
t.Errorf("got error %v, wantErr %v", err, tt.wantErr)
}
})
}
}
```
### Test Helpers
```go
func testDB(t *testing.T) *sql.DB {
t.Helper()
db, err := sql.Open("sqlite3", ":memory:")
if err != nil {
t.Fatalf("failed to open test db: %v", err)
}
t.Cleanup(func() { db.Close() })
return db
}
```
## When to Use This Skill
- Designing Go APIs and packages
- Implementing concurrent systems
- Structuring Go projects
- Writing idiomatic Go code
- Refactoring Go codebases

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@@ -0,0 +1,332 @@
---
name: golang-testing
description: >
Go testing best practices including table-driven tests, test helpers,
benchmarking, race detection, coverage analysis, and integration testing
patterns. Use when writing or improving Go tests.
metadata:
origin: ECC
globs: ["**/*.go", "**/go.mod", "**/go.sum"]
---
# Go Testing
> This skill provides comprehensive Go testing patterns extending common testing principles with Go-specific idioms.
## Testing Framework
Use the standard `go test` with **table-driven tests** as the primary pattern.
### Table-Driven Tests
The idiomatic Go testing pattern:
```go
func TestValidateEmail(t *testing.T) {
tests := []struct {
name string
email string
wantErr bool
}{
{
name: "valid email",
email: "user@example.com",
wantErr: false,
},
{
name: "missing @",
email: "userexample.com",
wantErr: true,
},
{
name: "empty string",
email: "",
wantErr: true,
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
err := ValidateEmail(tt.email)
if (err != nil) != tt.wantErr {
t.Errorf("ValidateEmail(%q) error = %v, wantErr %v",
tt.email, err, tt.wantErr)
}
})
}
}
```
**Benefits:**
- Easy to add new test cases
- Clear test case documentation
- Parallel test execution with `t.Parallel()`
- Isolated subtests with `t.Run()`
## Test Helpers
Use `t.Helper()` to mark helper functions:
```go
func assertNoError(t *testing.T, err error) {
t.Helper()
if err != nil {
t.Fatalf("unexpected error: %v", err)
}
}
func assertEqual(t *testing.T, got, want interface{}) {
t.Helper()
if !reflect.DeepEqual(got, want) {
t.Errorf("got %v, want %v", got, want)
}
}
```
**Benefits:**
- Correct line numbers in test failures
- Reusable test utilities
- Cleaner test code
## Test Fixtures
Use `t.Cleanup()` for resource cleanup:
```go
func testDB(t *testing.T) *sql.DB {
t.Helper()
db, err := sql.Open("sqlite3", ":memory:")
if err != nil {
t.Fatalf("failed to open test db: %v", err)
}
// Cleanup runs after test completes
t.Cleanup(func() {
if err := db.Close(); err != nil {
t.Errorf("failed to close db: %v", err)
}
})
return db
}
func TestUserRepository(t *testing.T) {
db := testDB(t)
repo := NewUserRepository(db)
// ... test logic
}
```
## Race Detection
Always run tests with the `-race` flag to detect data races:
```bash
go test -race ./...
```
**In CI/CD:**
```yaml
- name: Test with race detector
run: go test -race -timeout 5m ./...
```
**Why:**
- Detects concurrent access bugs
- Prevents production race conditions
- Minimal performance overhead in tests
## Coverage Analysis
### Basic Coverage
```bash
go test -cover ./...
```
### Detailed Coverage Report
```bash
go test -coverprofile=coverage.out ./...
go tool cover -html=coverage.out
```
### Coverage Thresholds
```bash
# Fail if coverage below 80%
go test -cover ./... | grep -E 'coverage: [0-7][0-9]\.[0-9]%' && exit 1
```
## Benchmarking
```go
func BenchmarkValidateEmail(b *testing.B) {
email := "user@example.com"
b.ResetTimer()
for i := 0; i < b.N; i++ {
ValidateEmail(email)
}
}
```
**Run benchmarks:**
```bash
go test -bench=. -benchmem
```
**Compare benchmarks:**
```bash
go test -bench=. -benchmem > old.txt
# make changes
go test -bench=. -benchmem > new.txt
benchstat old.txt new.txt
```
## Mocking
### Interface-Based Mocking
```go
type UserRepository interface {
GetUser(id string) (*User, error)
}
type mockUserRepository struct {
users map[string]*User
err error
}
func (m *mockUserRepository) GetUser(id string) (*User, error) {
if m.err != nil {
return nil, m.err
}
return m.users[id], nil
}
func TestUserService(t *testing.T) {
mock := &mockUserRepository{
users: map[string]*User{
"1": {ID: "1", Name: "Alice"},
},
}
service := NewUserService(mock)
// ... test logic
}
```
## Integration Tests
### Build Tags
```go
//go:build integration
// +build integration
package user_test
func TestUserRepository_Integration(t *testing.T) {
// ... integration test
}
```
**Run integration tests:**
```bash
go test -tags=integration ./...
```
### Test Containers
```go
func TestWithPostgres(t *testing.T) {
if testing.Short() {
t.Skip("skipping integration test")
}
// Setup test container
ctx := context.Background()
container, err := testcontainers.GenericContainer(ctx, ...)
assertNoError(t, err)
t.Cleanup(func() {
container.Terminate(ctx)
})
// ... test logic
}
```
## Test Organization
### File Structure
```
package/
├── user.go
├── user_test.go # Unit tests
├── user_integration_test.go # Integration tests
└── testdata/ # Test fixtures
└── users.json
```
### Package Naming
```go
// Black-box testing (external perspective)
package user_test
// White-box testing (internal access)
package user
```
## Common Patterns
### Testing HTTP Handlers
```go
func TestUserHandler(t *testing.T) {
req := httptest.NewRequest("GET", "/users/1", nil)
rec := httptest.NewRecorder()
handler := NewUserHandler(mockRepo)
handler.ServeHTTP(rec, req)
assertEqual(t, rec.Code, http.StatusOK)
}
```
### Testing with Context
```go
func TestWithTimeout(t *testing.T) {
ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
defer cancel()
err := SlowOperation(ctx)
if !errors.Is(err, context.DeadlineExceeded) {
t.Errorf("expected timeout error, got %v", err)
}
}
```
## Best Practices
1. **Use `t.Parallel()`** for independent tests
2. **Use `testing.Short()`** to skip slow tests
3. **Use `t.TempDir()`** for temporary directories
4. **Use `t.Setenv()`** for environment variables
5. **Avoid `init()`** in test files
6. **Keep tests focused** - one behavior per test
7. **Use meaningful test names** - describe what's being tested
## When to Use This Skill
- Writing new Go tests
- Improving test coverage
- Setting up test infrastructure
- Debugging flaky tests
- Optimizing test performance
- Implementing integration tests

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---
name: postgres-patterns
description: >
PostgreSQL database patterns for query optimization, schema design, indexing,
and security. Quick reference for common patterns, index types, data types,
and anti-pattern detection. Based on Supabase best practices.
metadata:
origin: ECC
credit: Supabase team (MIT License)
---
# PostgreSQL Patterns
Quick reference for PostgreSQL best practices. For detailed guidance, use the `database-reviewer` agent.
## When to Activate
- Writing SQL queries or migrations
- Designing database schemas
- Troubleshooting slow queries
- Implementing Row Level Security
- Setting up connection pooling
## Quick Reference
### Index Cheat Sheet
| Query Pattern | Index Type | Example |
|--------------|------------|---------|
| `WHERE col = value` | B-tree (default) | `CREATE INDEX idx ON t (col)` |
| `WHERE col > value` | B-tree | `CREATE INDEX idx ON t (col)` |
| `WHERE a = x AND b > y` | Composite | `CREATE INDEX idx ON t (a, b)` |
| `WHERE jsonb @> '{}'` | GIN | `CREATE INDEX idx ON t USING gin (col)` |
| `WHERE tsv @@ query` | GIN | `CREATE INDEX idx ON t USING gin (col)` |
| Time-series ranges | BRIN | `CREATE INDEX idx ON t USING brin (col)` |
### Data Type Quick Reference
| Use Case | Correct Type | Avoid |
|----------|-------------|-------|
| IDs | `bigint` | `int`, random UUID |
| Strings | `text` | `varchar(255)` |
| Timestamps | `timestamptz` | `timestamp` |
| Money | `numeric(10,2)` | `float` |
| Flags | `boolean` | `varchar`, `int` |
### Common Patterns
**Composite Index Order:**
```sql
-- Equality columns first, then range columns
CREATE INDEX idx ON orders (status, created_at);
-- Works for: WHERE status = 'pending' AND created_at > '2024-01-01'
```
**Covering Index:**
```sql
CREATE INDEX idx ON users (email) INCLUDE (name, created_at);
-- Avoids table lookup for SELECT email, name, created_at
```
**Partial Index:**
```sql
CREATE INDEX idx ON users (email) WHERE deleted_at IS NULL;
-- Smaller index, only includes active users
```
**RLS Policy (Optimized):**
```sql
CREATE POLICY policy ON orders
USING ((SELECT auth.uid()) = user_id); -- Wrap in SELECT!
```
**UPSERT:**
```sql
INSERT INTO settings (user_id, key, value)
VALUES (123, 'theme', 'dark')
ON CONFLICT (user_id, key)
DO UPDATE SET value = EXCLUDED.value;
```
**Cursor Pagination:**
```sql
SELECT * FROM products WHERE id > $last_id ORDER BY id LIMIT 20;
-- O(1) vs OFFSET which is O(n)
```
**Queue Processing:**
```sql
UPDATE jobs SET status = 'processing'
WHERE id = (
SELECT id FROM jobs WHERE status = 'pending'
ORDER BY created_at LIMIT 1
FOR UPDATE SKIP LOCKED
) RETURNING *;
```
### Anti-Pattern Detection
```sql
-- Find unindexed foreign keys
SELECT conrelid::regclass, a.attname
FROM pg_constraint c
JOIN pg_attribute a ON a.attrelid = c.conrelid AND a.attnum = ANY(c.conkey)
WHERE c.contype = 'f'
AND NOT EXISTS (
SELECT 1 FROM pg_index i
WHERE i.indrelid = c.conrelid AND a.attnum = ANY(i.indkey)
);
-- Find slow queries
SELECT query, mean_exec_time, calls
FROM pg_stat_statements
WHERE mean_exec_time > 100
ORDER BY mean_exec_time DESC;
-- Check table bloat
SELECT relname, n_dead_tup, last_vacuum
FROM pg_stat_user_tables
WHERE n_dead_tup > 1000
ORDER BY n_dead_tup DESC;
```
### Configuration Template
```sql
-- Connection limits (adjust for RAM)
ALTER SYSTEM SET max_connections = 100;
ALTER SYSTEM SET work_mem = '8MB';
-- Timeouts
ALTER SYSTEM SET idle_in_transaction_session_timeout = '30s';
ALTER SYSTEM SET statement_timeout = '30s';
-- Monitoring
CREATE EXTENSION IF NOT EXISTS pg_stat_statements;
-- Security defaults
REVOKE ALL ON SCHEMA public FROM public;
SELECT pg_reload_conf();
```
## Related
- Agent: `database-reviewer` - Full database review workflow
- Skill: `backend-patterns` - API and backend patterns
- Skill: `database-migrations` - Safe schema changes
## When to Use This Skill
- Writing SQL queries
- Designing database schemas
- Optimizing query performance
- Implementing Row Level Security
- Troubleshooting database issues
- Setting up PostgreSQL configuration
---
*Based on Supabase Agent Skills (credit: Supabase team) (MIT License)*

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---
name: python-patterns
description: >
Python-specific design patterns and best practices including protocols,
dataclasses, context managers, decorators, async/await, type hints, and
package organization. Use when working with Python code to apply Pythonic
patterns.
metadata:
origin: ECC
globs: ["**/*.py", "**/*.pyi"]
---
# Python Patterns
> This skill provides comprehensive Python patterns extending common design principles with Python-specific idioms.
## Protocol (Duck Typing)
Use `Protocol` for structural subtyping (duck typing with type hints):
```python
from typing import Protocol
class Repository(Protocol):
def find_by_id(self, id: str) -> dict | None: ...
def save(self, entity: dict) -> dict: ...
# Any class with these methods satisfies the protocol
class UserRepository:
def find_by_id(self, id: str) -> dict | None:
# implementation
pass
def save(self, entity: dict) -> dict:
# implementation
pass
def process_entity(repo: Repository, id: str) -> None:
entity = repo.find_by_id(id)
# ... process
```
**Benefits:**
- Type safety without inheritance
- Flexible, loosely coupled code
- Easy testing and mocking
## Dataclasses as DTOs
Use `dataclass` for data transfer objects and value objects:
```python
from dataclasses import dataclass, field
from typing import Optional
@dataclass
class CreateUserRequest:
name: str
email: str
age: Optional[int] = None
tags: list[str] = field(default_factory=list)
@dataclass(frozen=True)
class User:
"""Immutable user entity"""
id: str
name: str
email: str
```
**Features:**
- Auto-generated `__init__`, `__repr__`, `__eq__`
- `frozen=True` for immutability
- `field()` for complex defaults
- Type hints for validation
## Context Managers
Use context managers (`with` statement) for resource management:
```python
from contextlib import contextmanager
from typing import Generator
@contextmanager
def database_transaction(db) -> Generator[None, None, None]:
"""Context manager for database transactions"""
try:
yield
db.commit()
except Exception:
db.rollback()
raise
# Usage
with database_transaction(db):
db.execute("INSERT INTO users ...")
```
**Class-based context manager:**
```python
class FileProcessor:
def __init__(self, filename: str):
self.filename = filename
self.file = None
def __enter__(self):
self.file = open(self.filename, 'r')
return self.file
def __exit__(self, exc_type, exc_val, exc_tb):
if self.file:
self.file.close()
return False # Don't suppress exceptions
```
## Generators
Use generators for lazy evaluation and memory-efficient iteration:
```python
def read_large_file(filename: str):
"""Generator for reading large files line by line"""
with open(filename, 'r') as f:
for line in f:
yield line.strip()
# Memory-efficient processing
for line in read_large_file('huge.txt'):
process(line)
```
**Generator expressions:**
```python
# Instead of list comprehension
squares = (x**2 for x in range(1000000)) # Lazy evaluation
# Pipeline pattern
numbers = (x for x in range(100))
evens = (x for x in numbers if x % 2 == 0)
squares = (x**2 for x in evens)
```
## Decorators
### Function Decorators
```python
from functools import wraps
import time
def timing(func):
"""Decorator to measure execution time"""
@wraps(func)
def wrapper(*args, **kwargs):
start = time.time()
result = func(*args, **kwargs)
end = time.time()
print(f"{func.__name__} took {end - start:.2f}s")
return result
return wrapper
@timing
def slow_function():
time.sleep(1)
```
### Class Decorators
```python
def singleton(cls):
"""Decorator to make a class a singleton"""
instances = {}
@wraps(cls)
def get_instance(*args, **kwargs):
if cls not in instances:
instances[cls] = cls(*args, **kwargs)
return instances[cls]
return get_instance
@singleton
class Config:
pass
```
## Async/Await
### Async Functions
```python
import asyncio
from typing import List
async def fetch_user(user_id: str) -> dict:
"""Async function for I/O-bound operations"""
await asyncio.sleep(0.1) # Simulate network call
return {"id": user_id, "name": "Alice"}
async def fetch_all_users(user_ids: List[str]) -> List[dict]:
"""Concurrent execution with asyncio.gather"""
tasks = [fetch_user(uid) for uid in user_ids]
return await asyncio.gather(*tasks)
# Run async code
asyncio.run(fetch_all_users(["1", "2", "3"]))
```
### Async Context Managers
```python
class AsyncDatabase:
async def __aenter__(self):
await self.connect()
return self
async def __aexit__(self, exc_type, exc_val, exc_tb):
await self.disconnect()
async with AsyncDatabase() as db:
await db.query("SELECT * FROM users")
```
## Type Hints
### Advanced Type Hints
```python
from typing import TypeVar, Generic, Callable, ParamSpec, Concatenate
T = TypeVar('T')
P = ParamSpec('P')
class Repository(Generic[T]):
"""Generic repository pattern"""
def __init__(self, entity_type: type[T]):
self.entity_type = entity_type
def find_by_id(self, id: str) -> T | None:
# implementation
pass
# Type-safe decorator
def log_call(func: Callable[P, T]) -> Callable[P, T]:
@wraps(func)
def wrapper(*args: P.args, **kwargs: P.kwargs) -> T:
print(f"Calling {func.__name__}")
return func(*args, **kwargs)
return wrapper
```
### Union Types (Python 3.10+)
```python
def process(value: str | int | None) -> str:
match value:
case str():
return value.upper()
case int():
return str(value)
case None:
return "empty"
```
## Dependency Injection
### Constructor Injection
```python
class UserService:
def __init__(
self,
repository: Repository,
logger: Logger,
cache: Cache | None = None
):
self.repository = repository
self.logger = logger
self.cache = cache
def get_user(self, user_id: str) -> User | None:
if self.cache:
cached = self.cache.get(user_id)
if cached:
return cached
user = self.repository.find_by_id(user_id)
if user and self.cache:
self.cache.set(user_id, user)
return user
```
## Package Organization
### Project Structure
```
project/
├── src/
│ └── mypackage/
│ ├── __init__.py
│ ├── domain/ # Business logic
│ │ ├── __init__.py
│ │ └── models.py
│ ├── services/ # Application services
│ │ ├── __init__.py
│ │ └── user_service.py
│ └── infrastructure/ # External dependencies
│ ├── __init__.py
│ └── database.py
├── tests/
│ ├── unit/
│ └── integration/
├── pyproject.toml
└── README.md
```
### Module Exports
```python
# __init__.py
from .models import User, Product
from .services import UserService
__all__ = ['User', 'Product', 'UserService']
```
## Error Handling
### Custom Exceptions
```python
class DomainError(Exception):
"""Base exception for domain errors"""
pass
class UserNotFoundError(DomainError):
"""Raised when user is not found"""
def __init__(self, user_id: str):
self.user_id = user_id
super().__init__(f"User {user_id} not found")
class ValidationError(DomainError):
"""Raised when validation fails"""
def __init__(self, field: str, message: str):
self.field = field
self.message = message
super().__init__(f"{field}: {message}")
```
### Exception Groups (Python 3.11+)
```python
try:
# Multiple operations
pass
except* ValueError as eg:
# Handle all ValueError instances
for exc in eg.exceptions:
print(f"ValueError: {exc}")
except* TypeError as eg:
# Handle all TypeError instances
for exc in eg.exceptions:
print(f"TypeError: {exc}")
```
## Property Decorators
```python
class User:
def __init__(self, name: str):
self._name = name
self._email = None
@property
def name(self) -> str:
"""Read-only property"""
return self._name
@property
def email(self) -> str | None:
return self._email
@email.setter
def email(self, value: str) -> None:
if '@' not in value:
raise ValueError("Invalid email")
self._email = value
```
## Functional Programming
### Higher-Order Functions
```python
from functools import reduce
from typing import Callable, TypeVar
T = TypeVar('T')
U = TypeVar('U')
def pipe(*functions: Callable) -> Callable:
"""Compose functions left to right"""
def inner(arg):
return reduce(lambda x, f: f(x), functions, arg)
return inner
# Usage
process = pipe(
str.strip,
str.lower,
lambda s: s.replace(' ', '_')
)
result = process(" Hello World ") # "hello_world"
```
## When to Use This Skill
- Designing Python APIs and packages
- Implementing async/concurrent systems
- Structuring Python projects
- Writing Pythonic code
- Refactoring Python codebases
- Type-safe Python development

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---
name: python-testing
description: >
Python testing best practices using pytest including fixtures, parametrization,
mocking, coverage analysis, async testing, and test organization. Use when
writing or improving Python tests.
metadata:
origin: ECC
globs: ["**/*.py", "**/*.pyi"]
---
# Python Testing
> This skill provides comprehensive Python testing patterns using pytest as the primary testing framework.
## Testing Framework
Use **pytest** as the testing framework for its powerful features and clean syntax.
### Basic Test Structure
```python
def test_user_creation():
"""Test that a user can be created with valid data"""
user = User(name="Alice", email="alice@example.com")
assert user.name == "Alice"
assert user.email == "alice@example.com"
assert user.is_active is True
```
### Test Discovery
pytest automatically discovers tests following these conventions:
- Files: `test_*.py` or `*_test.py`
- Functions: `test_*`
- Classes: `Test*` (without `__init__`)
- Methods: `test_*`
## Fixtures
Fixtures provide reusable test setup and teardown:
```python
import pytest
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
@pytest.fixture
def db_session():
"""Provide a database session for tests"""
engine = create_engine("sqlite:///:memory:")
Session = sessionmaker(bind=engine)
session = Session()
# Setup
Base.metadata.create_all(engine)
yield session
# Teardown
session.close()
def test_user_repository(db_session):
"""Test using the db_session fixture"""
repo = UserRepository(db_session)
user = repo.create(name="Alice", email="alice@example.com")
assert user.id is not None
```
### Fixture Scopes
```python
@pytest.fixture(scope="function") # Default: per test
def user():
return User(name="Alice")
@pytest.fixture(scope="class") # Per test class
def database():
db = Database()
db.connect()
yield db
db.disconnect()
@pytest.fixture(scope="module") # Per module
def app():
return create_app()
@pytest.fixture(scope="session") # Once per test session
def config():
return load_config()
```
### Fixture Dependencies
```python
@pytest.fixture
def database():
db = Database()
db.connect()
yield db
db.disconnect()
@pytest.fixture
def user_repository(database):
"""Fixture that depends on database fixture"""
return UserRepository(database)
def test_create_user(user_repository):
user = user_repository.create(name="Alice")
assert user.id is not None
```
## Parametrization
Test multiple inputs with `@pytest.mark.parametrize`:
```python
import pytest
@pytest.mark.parametrize("email,expected", [
("user@example.com", True),
("invalid-email", False),
("", False),
("user@", False),
("@example.com", False),
])
def test_email_validation(email, expected):
result = validate_email(email)
assert result == expected
```
### Multiple Parameters
```python
@pytest.mark.parametrize("name,age,valid", [
("Alice", 25, True),
("Bob", 17, False),
("", 25, False),
("Charlie", -1, False),
])
def test_user_validation(name, age, valid):
result = validate_user(name, age)
assert result == valid
```
### Parametrize with IDs
```python
@pytest.mark.parametrize("input,expected", [
("hello", "HELLO"),
("world", "WORLD"),
], ids=["lowercase", "another_lowercase"])
def test_uppercase(input, expected):
assert input.upper() == expected
```
## Test Markers
Use markers for test categorization and selective execution:
```python
import pytest
@pytest.mark.unit
def test_calculate_total():
"""Fast unit test"""
assert calculate_total([1, 2, 3]) == 6
@pytest.mark.integration
def test_database_connection():
"""Slower integration test"""
db = Database()
assert db.connect() is True
@pytest.mark.slow
def test_large_dataset():
"""Very slow test"""
process_million_records()
@pytest.mark.skip(reason="Not implemented yet")
def test_future_feature():
pass
@pytest.mark.skipif(sys.version_info < (3, 10), reason="Requires Python 3.10+")
def test_new_syntax():
pass
```
**Run specific markers:**
```bash
pytest -m unit # Run only unit tests
pytest -m "not slow" # Skip slow tests
pytest -m "unit or integration" # Run unit OR integration
```
## Mocking
### Using unittest.mock
```python
from unittest.mock import Mock, patch, MagicMock
def test_user_service_with_mock():
"""Test with mock repository"""
mock_repo = Mock()
mock_repo.find_by_id.return_value = User(id="1", name="Alice")
service = UserService(mock_repo)
user = service.get_user("1")
assert user.name == "Alice"
mock_repo.find_by_id.assert_called_once_with("1")
@patch('myapp.services.EmailService')
def test_send_notification(mock_email_service):
"""Test with patched dependency"""
service = NotificationService()
service.send("user@example.com", "Hello")
mock_email_service.send.assert_called_once()
```
### pytest-mock Plugin
```python
def test_with_mocker(mocker):
"""Using pytest-mock plugin"""
mock_repo = mocker.Mock()
mock_repo.find_by_id.return_value = User(id="1", name="Alice")
service = UserService(mock_repo)
user = service.get_user("1")
assert user.name == "Alice"
```
## Coverage Analysis
### Basic Coverage
```bash
pytest --cov=src --cov-report=term-missing
```
### HTML Coverage Report
```bash
pytest --cov=src --cov-report=html
open htmlcov/index.html
```
### Coverage Configuration
```ini
# pytest.ini or pyproject.toml
[tool.pytest.ini_options]
addopts = """
--cov=src
--cov-report=term-missing
--cov-report=html
--cov-fail-under=80
"""
```
### Branch Coverage
```bash
pytest --cov=src --cov-branch
```
## Async Testing
### Testing Async Functions
```python
import pytest
@pytest.mark.asyncio
async def test_async_fetch_user():
"""Test async function"""
user = await fetch_user("1")
assert user.name == "Alice"
@pytest.fixture
async def async_client():
"""Async fixture"""
client = AsyncClient()
await client.connect()
yield client
await client.disconnect()
@pytest.mark.asyncio
async def test_with_async_fixture(async_client):
result = await async_client.get("/users/1")
assert result.status == 200
```
## Test Organization
### Directory Structure
```
tests/
├── unit/
│ ├── test_models.py
│ ├── test_services.py
│ └── test_utils.py
├── integration/
│ ├── test_database.py
│ └── test_api.py
├── conftest.py # Shared fixtures
└── pytest.ini # Configuration
```
### conftest.py
```python
# tests/conftest.py
import pytest
@pytest.fixture(scope="session")
def app():
"""Application fixture available to all tests"""
return create_app()
@pytest.fixture
def client(app):
"""Test client fixture"""
return app.test_client()
def pytest_configure(config):
"""Register custom markers"""
config.addinivalue_line("markers", "unit: Unit tests")
config.addinivalue_line("markers", "integration: Integration tests")
config.addinivalue_line("markers", "slow: Slow tests")
```
## Assertions
### Basic Assertions
```python
def test_assertions():
assert value == expected
assert value != other
assert value > 0
assert value in collection
assert isinstance(value, str)
```
### pytest Assertions with Better Error Messages
```python
def test_with_context():
"""pytest provides detailed assertion introspection"""
result = calculate_total([1, 2, 3])
expected = 6
# pytest shows: assert 5 == 6
assert result == expected
```
### Custom Assertion Messages
```python
def test_with_message():
result = process_data(input_data)
assert result.is_valid, f"Expected valid result, got errors: {result.errors}"
```
### Approximate Comparisons
```python
import pytest
def test_float_comparison():
result = 0.1 + 0.2
assert result == pytest.approx(0.3)
# With tolerance
assert result == pytest.approx(0.3, abs=1e-9)
```
## Exception Testing
```python
import pytest
def test_raises_exception():
"""Test that function raises expected exception"""
with pytest.raises(ValueError):
validate_age(-1)
def test_exception_message():
"""Test exception message"""
with pytest.raises(ValueError, match="Age must be positive"):
validate_age(-1)
def test_exception_details():
"""Capture and inspect exception"""
with pytest.raises(ValidationError) as exc_info:
validate_user(name="", age=-1)
assert "name" in exc_info.value.errors
assert "age" in exc_info.value.errors
```
## Test Helpers
```python
# tests/helpers.py
def assert_user_equal(actual, expected):
"""Custom assertion helper"""
assert actual.id == expected.id
assert actual.name == expected.name
assert actual.email == expected.email
def create_test_user(**kwargs):
"""Test data factory"""
defaults = {
"name": "Test User",
"email": "test@example.com",
"age": 25,
}
defaults.update(kwargs)
return User(**defaults)
```
## Property-Based Testing
Using `hypothesis` for property-based testing:
```python
from hypothesis import given, strategies as st
@given(st.integers(), st.integers())
def test_addition_commutative(a, b):
"""Test that addition is commutative"""
assert a + b == b + a
@given(st.lists(st.integers()))
def test_sort_idempotent(lst):
"""Test that sorting twice gives same result"""
sorted_once = sorted(lst)
sorted_twice = sorted(sorted_once)
assert sorted_once == sorted_twice
```
## Best Practices
1. **One assertion per test** (when possible)
2. **Use descriptive test names** - describe what's being tested
3. **Arrange-Act-Assert pattern** - clear test structure
4. **Use fixtures for setup** - avoid duplication
5. **Mock external dependencies** - keep tests fast and isolated
6. **Test edge cases** - empty inputs, None, boundaries
7. **Use parametrize** - test multiple scenarios efficiently
8. **Keep tests independent** - no shared state between tests
## Running Tests
```bash
# Run all tests
pytest
# Run specific file
pytest tests/test_user.py
# Run specific test
pytest tests/test_user.py::test_create_user
# Run with verbose output
pytest -v
# Run with output capture disabled
pytest -s
# Run in parallel (requires pytest-xdist)
pytest -n auto
# Run only failed tests from last run
pytest --lf
# Run failed tests first
pytest --ff
```
## When to Use This Skill
- Writing new Python tests
- Improving test coverage
- Setting up pytest infrastructure
- Debugging flaky tests
- Implementing integration tests
- Testing async Python code

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---
name: search-first
description: >
Research-before-coding workflow. Search for existing tools, libraries, and
patterns before writing custom code. Systematizes the "search for existing
solutions before implementing" approach. Use when starting new features or
adding functionality.
metadata:
origin: ECC
---
# /search-first — Research Before You Code
Systematizes the "search for existing solutions before implementing" workflow.
## Trigger
Use this skill when:
- Starting a new feature that likely has existing solutions
- Adding a dependency or integration
- The user asks "add X functionality" and you're about to write code
- Before creating a new utility, helper, or abstraction
## Workflow
```
┌─────────────────────────────────────────────┐
│ 1. NEED ANALYSIS │
│ Define what functionality is needed │
│ Identify language/framework constraints │
├─────────────────────────────────────────────┤
│ 2. PARALLEL SEARCH (researcher agent) │
│ ┌──────────┐ ┌──────────┐ ┌──────────┐ │
│ │ npm / │ │ MCP / │ │ GitHub / │ │
│ │ PyPI │ │ Skills │ │ Web │ │
│ └──────────┘ └──────────┘ └──────────┘ │
├─────────────────────────────────────────────┤
│ 3. EVALUATE │
│ Score candidates (functionality, maint, │
│ community, docs, license, deps) │
├─────────────────────────────────────────────┤
│ 4. DECIDE │
│ ┌─────────┐ ┌──────────┐ ┌─────────┐ │
│ │ Adopt │ │ Extend │ │ Build │ │
│ │ as-is │ │ /Wrap │ │ Custom │ │
│ └─────────┘ └──────────┘ └─────────┘ │
├─────────────────────────────────────────────┤
│ 5. IMPLEMENT │
│ Install package / Configure MCP / │
│ Write minimal custom code │
└─────────────────────────────────────────────┘
```
## Decision Matrix
| Signal | Action |
|--------|--------|
| Exact match, well-maintained, MIT/Apache | **Adopt** — install and use directly |
| Partial match, good foundation | **Extend** — install + write thin wrapper |
| Multiple weak matches | **Compose** — combine 2-3 small packages |
| Nothing suitable found | **Build** — write custom, but informed by research |
## How to Use
### Quick Mode (inline)
Before writing a utility or adding functionality, mentally run through:
0. Does this already exist in the repo? → Search through relevant modules/tests first
1. Is this a common problem? → Search npm/PyPI
2. Is there an MCP for this? → Check MCP configuration and search
3. Is there a skill for this? → Check available skills
4. Is there a GitHub implementation/template? → Run GitHub code search for maintained OSS before writing net-new code
### Full Mode (subagent)
For non-trivial functionality, delegate to a research-focused subagent:
```
Invoke subagent with prompt:
"Research existing tools for: [DESCRIPTION]
Language/framework: [LANG]
Constraints: [ANY]
Search: npm/PyPI, MCP servers, skills, GitHub
Return: Structured comparison with recommendation"
```
## Search Shortcuts by Category
### Development Tooling
- Linting → `eslint`, `ruff`, `textlint`, `markdownlint`
- Formatting → `prettier`, `black`, `gofmt`
- Testing → `jest`, `pytest`, `go test`
- Pre-commit → `husky`, `lint-staged`, `pre-commit`
### AI/LLM Integration
- Claude SDK → Check for latest docs
- Prompt management → Check MCP servers
- Document processing → `unstructured`, `pdfplumber`, `mammoth`
### Data & APIs
- HTTP clients → `httpx` (Python), `ky`/`got` (Node)
- Validation → `zod` (TS), `pydantic` (Python)
- Database → Check for MCP servers first
### Content & Publishing
- Markdown processing → `remark`, `unified`, `markdown-it`
- Image optimization → `sharp`, `imagemin`
## Integration Points
### With planner agent
The planner should invoke researcher before Phase 1 (Architecture Review):
- Researcher identifies available tools
- Planner incorporates them into the implementation plan
- Avoids "reinventing the wheel" in the plan
### With architect agent
The architect should consult researcher for:
- Technology stack decisions
- Integration pattern discovery
- Existing reference architectures
### With iterative-retrieval skill
Combine for progressive discovery:
- Cycle 1: Broad search (npm, PyPI, MCP)
- Cycle 2: Evaluate top candidates in detail
- Cycle 3: Test compatibility with project constraints
## Examples
### Example 1: "Add dead link checking"
```
Need: Check markdown files for broken links
Search: npm "markdown dead link checker"
Found: textlint-rule-no-dead-link (score: 9/10)
Action: ADOPT — npm install textlint-rule-no-dead-link
Result: Zero custom code, battle-tested solution
```
### Example 2: "Add HTTP client wrapper"
```
Need: Resilient HTTP client with retries and timeout handling
Search: npm "http client retry", PyPI "httpx retry"
Found: got (Node) with retry plugin, httpx (Python) with built-in retry
Action: ADOPT — use got/httpx directly with retry config
Result: Zero custom code, production-proven libraries
```
### Example 3: "Add config file linter"
```
Need: Validate project config files against a schema
Search: npm "config linter schema", "json schema validator cli"
Found: ajv-cli (score: 8/10)
Action: ADOPT + EXTEND — install ajv-cli, write project-specific schema
Result: 1 package + 1 schema file, no custom validation logic
```
## Anti-Patterns
- **Jumping to code**: Writing a utility without checking if one exists
- **Ignoring MCP**: Not checking if an MCP server already provides the capability
- **Over-customizing**: Wrapping a library so heavily it loses its benefits
- **Dependency bloat**: Installing a massive package for one small feature
## When to Use This Skill
- Starting new features
- Adding dependencies or integrations
- Before writing utilities or helpers
- When evaluating technology choices
- Planning architecture decisions

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@@ -0,0 +1,497 @@
---
name: security-review
description: >
Use this skill when adding authentication, handling user input, working with secrets, creating API endpoints, or implementing payment/sensitive features. Provides comprehensive security checklist and patterns.
metadata:
origin: ECC
---
# Security Review Skill
This skill ensures all code follows security best practices and identifies potential vulnerabilities.
## When to Activate
- Implementing authentication or authorization
- Handling user input or file uploads
- Creating new API endpoints
- Working with secrets or credentials
- Implementing payment features
- Storing or transmitting sensitive data
- Integrating third-party APIs
## Security Checklist
### 1. Secrets Management
#### ❌ NEVER Do This
```typescript
const apiKey = "sk-proj-xxxxx" // Hardcoded secret
const dbPassword = "password123" // In source code
```
#### ✅ ALWAYS Do This
```typescript
const apiKey = process.env.OPENAI_API_KEY
const dbUrl = process.env.DATABASE_URL
// Verify secrets exist
if (!apiKey) {
throw new Error('OPENAI_API_KEY not configured')
}
```
#### Verification Steps
- [ ] No hardcoded API keys, tokens, or passwords
- [ ] All secrets in environment variables
- [ ] `.env.local` in .gitignore
- [ ] No secrets in git history
- [ ] Production secrets in hosting platform (Vercel, Railway)
### 2. Input Validation
#### Always Validate User Input
```typescript
import { z } from 'zod'
// Define validation schema
const CreateUserSchema = z.object({
email: z.string().email(),
name: z.string().min(1).max(100),
age: z.number().int().min(0).max(150)
})
// Validate before processing
export async function createUser(input: unknown) {
try {
const validated = CreateUserSchema.parse(input)
return await db.users.create(validated)
} catch (error) {
if (error instanceof z.ZodError) {
return { success: false, errors: error.errors }
}
throw error
}
}
```
#### File Upload Validation
```typescript
function validateFileUpload(file: File) {
// Size check (5MB max)
const maxSize = 5 * 1024 * 1024
if (file.size > maxSize) {
throw new Error('File too large (max 5MB)')
}
// Type check
const allowedTypes = ['image/jpeg', 'image/png', 'image/gif']
if (!allowedTypes.includes(file.type)) {
throw new Error('Invalid file type')
}
// Extension check
const allowedExtensions = ['.jpg', '.jpeg', '.png', '.gif']
const extension = file.name.toLowerCase().match(/\.[^.]+$/)?.[0]
if (!extension || !allowedExtensions.includes(extension)) {
throw new Error('Invalid file extension')
}
return true
}
```
#### Verification Steps
- [ ] All user inputs validated with schemas
- [ ] File uploads restricted (size, type, extension)
- [ ] No direct use of user input in queries
- [ ] Whitelist validation (not blacklist)
- [ ] Error messages don't leak sensitive info
### 3. SQL Injection Prevention
#### ❌ NEVER Concatenate SQL
```typescript
// DANGEROUS - SQL Injection vulnerability
const query = `SELECT * FROM users WHERE email = '${userEmail}'`
await db.query(query)
```
#### ✅ ALWAYS Use Parameterized Queries
```typescript
// Safe - parameterized query
const { data } = await supabase
.from('users')
.select('*')
.eq('email', userEmail)
// Or with raw SQL
await db.query(
'SELECT * FROM users WHERE email = $1',
[userEmail]
)
```
#### Verification Steps
- [ ] All database queries use parameterized queries
- [ ] No string concatenation in SQL
- [ ] ORM/query builder used correctly
- [ ] Supabase queries properly sanitized
### 4. Authentication & Authorization
#### JWT Token Handling
```typescript
// ❌ WRONG: localStorage (vulnerable to XSS)
localStorage.setItem('token', token)
// ✅ CORRECT: httpOnly cookies
res.setHeader('Set-Cookie',
`token=${token}; HttpOnly; Secure; SameSite=Strict; Max-Age=3600`)
```
#### Authorization Checks
```typescript
export async function deleteUser(userId: string, requesterId: string) {
// ALWAYS verify authorization first
const requester = await db.users.findUnique({
where: { id: requesterId }
})
if (requester.role !== 'admin') {
return NextResponse.json(
{ error: 'Unauthorized' },
{ status: 403 }
)
}
// Proceed with deletion
await db.users.delete({ where: { id: userId } })
}
```
#### Row Level Security (Supabase)
```sql
-- Enable RLS on all tables
ALTER TABLE users ENABLE ROW LEVEL SECURITY;
-- Users can only view their own data
CREATE POLICY "Users view own data"
ON users FOR SELECT
USING (auth.uid() = id);
-- Users can only update their own data
CREATE POLICY "Users update own data"
ON users FOR UPDATE
USING (auth.uid() = id);
```
#### Verification Steps
- [ ] Tokens stored in httpOnly cookies (not localStorage)
- [ ] Authorization checks before sensitive operations
- [ ] Row Level Security enabled in Supabase
- [ ] Role-based access control implemented
- [ ] Session management secure
### 5. XSS Prevention
#### Sanitize HTML
```typescript
import DOMPurify from 'isomorphic-dompurify'
// ALWAYS sanitize user-provided HTML
function renderUserContent(html: string) {
const clean = DOMPurify.sanitize(html, {
ALLOWED_TAGS: ['b', 'i', 'em', 'strong', 'p'],
ALLOWED_ATTR: []
})
return <div dangerouslySetInnerHTML={{ __html: clean }} />
}
```
#### Content Security Policy
```typescript
// next.config.js
const securityHeaders = [
{
key: 'Content-Security-Policy',
value: `
default-src 'self';
script-src 'self' 'unsafe-eval' 'unsafe-inline';
style-src 'self' 'unsafe-inline';
img-src 'self' data: https:;
font-src 'self';
connect-src 'self' https://api.example.com;
`.replace(/\s{2,}/g, ' ').trim()
}
]
```
#### Verification Steps
- [ ] User-provided HTML sanitized
- [ ] CSP headers configured
- [ ] No unvalidated dynamic content rendering
- [ ] React's built-in XSS protection used
### 6. CSRF Protection
#### CSRF Tokens
```typescript
import { csrf } from '@/lib/csrf'
export async function POST(request: Request) {
const token = request.headers.get('X-CSRF-Token')
if (!csrf.verify(token)) {
return NextResponse.json(
{ error: 'Invalid CSRF token' },
{ status: 403 }
)
}
// Process request
}
```
#### SameSite Cookies
```typescript
res.setHeader('Set-Cookie',
`session=${sessionId}; HttpOnly; Secure; SameSite=Strict`)
```
#### Verification Steps
- [ ] CSRF tokens on state-changing operations
- [ ] SameSite=Strict on all cookies
- [ ] Double-submit cookie pattern implemented
### 7. Rate Limiting
#### API Rate Limiting
```typescript
import rateLimit from 'express-rate-limit'
const limiter = rateLimit({
windowMs: 15 * 60 * 1000, // 15 minutes
max: 100, // 100 requests per window
message: 'Too many requests'
})
// Apply to routes
app.use('/api/', limiter)
```
#### Expensive Operations
```typescript
// Aggressive rate limiting for searches
const searchLimiter = rateLimit({
windowMs: 60 * 1000, // 1 minute
max: 10, // 10 requests per minute
message: 'Too many search requests'
})
app.use('/api/search', searchLimiter)
```
#### Verification Steps
- [ ] Rate limiting on all API endpoints
- [ ] Stricter limits on expensive operations
- [ ] IP-based rate limiting
- [ ] User-based rate limiting (authenticated)
### 8. Sensitive Data Exposure
#### Logging
```typescript
// ❌ WRONG: Logging sensitive data
console.log('User login:', { email, password })
console.log('Payment:', { cardNumber, cvv })
// ✅ CORRECT: Redact sensitive data
console.log('User login:', { email, userId })
console.log('Payment:', { last4: card.last4, userId })
```
#### Error Messages
```typescript
// ❌ WRONG: Exposing internal details
catch (error) {
return NextResponse.json(
{ error: error.message, stack: error.stack },
{ status: 500 }
)
}
// ✅ CORRECT: Generic error messages
catch (error) {
console.error('Internal error:', error)
return NextResponse.json(
{ error: 'An error occurred. Please try again.' },
{ status: 500 }
)
}
```
#### Verification Steps
- [ ] No passwords, tokens, or secrets in logs
- [ ] Error messages generic for users
- [ ] Detailed errors only in server logs
- [ ] No stack traces exposed to users
### 9. Blockchain Security (Solana)
#### Wallet Verification
```typescript
import { verify } from '@solana/web3.js'
async function verifyWalletOwnership(
publicKey: string,
signature: string,
message: string
) {
try {
const isValid = verify(
Buffer.from(message),
Buffer.from(signature, 'base64'),
Buffer.from(publicKey, 'base64')
)
return isValid
} catch (error) {
return false
}
}
```
#### Transaction Verification
```typescript
async function verifyTransaction(transaction: Transaction) {
// Verify recipient
if (transaction.to !== expectedRecipient) {
throw new Error('Invalid recipient')
}
// Verify amount
if (transaction.amount > maxAmount) {
throw new Error('Amount exceeds limit')
}
// Verify user has sufficient balance
const balance = await getBalance(transaction.from)
if (balance < transaction.amount) {
throw new Error('Insufficient balance')
}
return true
}
```
#### Verification Steps
- [ ] Wallet signatures verified
- [ ] Transaction details validated
- [ ] Balance checks before transactions
- [ ] No blind transaction signing
### 10. Dependency Security
#### Regular Updates
```bash
# Check for vulnerabilities
npm audit
# Fix automatically fixable issues
npm audit fix
# Update dependencies
npm update
# Check for outdated packages
npm outdated
```
#### Lock Files
```bash
# ALWAYS commit lock files
git add package-lock.json
# Use in CI/CD for reproducible builds
npm ci # Instead of npm install
```
#### Verification Steps
- [ ] Dependencies up to date
- [ ] No known vulnerabilities (npm audit clean)
- [ ] Lock files committed
- [ ] Dependabot enabled on GitHub
- [ ] Regular security updates
## Security Testing
### Automated Security Tests
```typescript
// Test authentication
test('requires authentication', async () => {
const response = await fetch('/api/protected')
expect(response.status).toBe(401)
})
// Test authorization
test('requires admin role', async () => {
const response = await fetch('/api/admin', {
headers: { Authorization: `Bearer ${userToken}` }
})
expect(response.status).toBe(403)
})
// Test input validation
test('rejects invalid input', async () => {
const response = await fetch('/api/users', {
method: 'POST',
body: JSON.stringify({ email: 'not-an-email' })
})
expect(response.status).toBe(400)
})
// Test rate limiting
test('enforces rate limits', async () => {
const requests = Array(101).fill(null).map(() =>
fetch('/api/endpoint')
)
const responses = await Promise.all(requests)
const tooManyRequests = responses.filter(r => r.status === 429)
expect(tooManyRequests.length).toBeGreaterThan(0)
})
```
## Pre-Deployment Security Checklist
Before ANY production deployment:
- [ ] **Secrets**: No hardcoded secrets, all in env vars
- [ ] **Input Validation**: All user inputs validated
- [ ] **SQL Injection**: All queries parameterized
- [ ] **XSS**: User content sanitized
- [ ] **CSRF**: Protection enabled
- [ ] **Authentication**: Proper token handling
- [ ] **Authorization**: Role checks in place
- [ ] **Rate Limiting**: Enabled on all endpoints
- [ ] **HTTPS**: Enforced in production
- [ ] **Security Headers**: CSP, X-Frame-Options configured
- [ ] **Error Handling**: No sensitive data in errors
- [ ] **Logging**: No sensitive data logged
- [ ] **Dependencies**: Up to date, no vulnerabilities
- [ ] **Row Level Security**: Enabled in Supabase
- [ ] **CORS**: Properly configured
- [ ] **File Uploads**: Validated (size, type)
- [ ] **Wallet Signatures**: Verified (if blockchain)
## Resources
- [OWASP Top 10](https://owasp.org/www-project-top-ten/)
- [Next.js Security](https://nextjs.org/docs/security)
- [Supabase Security](https://supabase.com/docs/guides/auth)
- [Web Security Academy](https://portswigger.net/web-security)
---
**Remember**: Security is not optional. One vulnerability can compromise the entire platform. When in doubt, err on the side of caution.

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---
name: tdd-workflow
description: >
Use this skill when writing new features, fixing bugs, or refactoring code.
Enforces test-driven development with 80%+ coverage including unit, integration, and E2E tests.
metadata:
origin: ECC
version: "1.0"
---
# Test-Driven Development Workflow
This skill ensures all code development follows TDD principles with comprehensive test coverage.
## When to Activate
- Writing new features or functionality
- Fixing bugs or issues
- Refactoring existing code
- Adding API endpoints
- Creating new components
## Core Principles
### 1. Tests BEFORE Code
ALWAYS write tests first, then implement code to make tests pass.
### 2. Coverage Requirements
- Minimum 80% coverage (unit + integration + E2E)
- All edge cases covered
- Error scenarios tested
- Boundary conditions verified
### 3. Test Types
#### Unit Tests
- Individual functions and utilities
- Component logic
- Pure functions
- Helpers and utilities
#### Integration Tests
- API endpoints
- Database operations
- Service interactions
- External API calls
#### E2E Tests (Playwright)
- Critical user flows
- Complete workflows
- Browser automation
- UI interactions
## TDD Workflow Steps
### Step 1: Write User Journeys
```
As a [role], I want to [action], so that [benefit]
Example:
As a user, I want to search for markets semantically,
so that I can find relevant markets even without exact keywords.
```
### Step 2: Generate Test Cases
For each user journey, create comprehensive test cases:
```typescript
describe('Semantic Search', () => {
it('returns relevant markets for query', async () => {
// Test implementation
})
it('handles empty query gracefully', async () => {
// Test edge case
})
it('falls back to substring search when Redis unavailable', async () => {
// Test fallback behavior
})
it('sorts results by similarity score', async () => {
// Test sorting logic
})
})
```
### Step 3: Run Tests (They Should Fail)
```bash
npm test
# Tests should fail - we haven't implemented yet
```
### Step 4: Implement Code
Write minimal code to make tests pass:
```typescript
// Implementation guided by tests
export async function searchMarkets(query: string) {
// Implementation here
}
```
### Step 5: Run Tests Again
```bash
npm test
# Tests should now pass
```
### Step 6: Refactor
Improve code quality while keeping tests green:
- Remove duplication
- Improve naming
- Optimize performance
- Enhance readability
### Step 7: Verify Coverage
```bash
npm run test:coverage
# Verify 80%+ coverage achieved
```
## Testing Patterns
### Unit Test Pattern (Jest/Vitest)
```typescript
import { render, screen, fireEvent } from '@testing-library/react'
import { Button } from './Button'
describe('Button Component', () => {
it('renders with correct text', () => {
render(<Button>Click me</Button>)
expect(screen.getByText('Click me')).toBeInTheDocument()
})
it('calls onClick when clicked', () => {
const handleClick = jest.fn()
render(<Button onClick={handleClick}>Click</Button>)
fireEvent.click(screen.getByRole('button'))
expect(handleClick).toHaveBeenCalledTimes(1)
})
it('is disabled when disabled prop is true', () => {
render(<Button disabled>Click</Button>)
expect(screen.getByRole('button')).toBeDisabled()
})
})
```
### API Integration Test Pattern
```typescript
import { NextRequest } from 'next/server'
import { GET } from './route'
describe('GET /api/markets', () => {
it('returns markets successfully', async () => {
const request = new NextRequest('http://localhost/api/markets')
const response = await GET(request)
const data = await response.json()
expect(response.status).toBe(200)
expect(data.success).toBe(true)
expect(Array.isArray(data.data)).toBe(true)
})
it('validates query parameters', async () => {
const request = new NextRequest('http://localhost/api/markets?limit=invalid')
const response = await GET(request)
expect(response.status).toBe(400)
})
it('handles database errors gracefully', async () => {
// Mock database failure
const request = new NextRequest('http://localhost/api/markets')
// Test error handling
})
})
```
### E2E Test Pattern (Playwright)
```typescript
import { test, expect } from '@playwright/test'
test('user can search and filter markets', async ({ page }) => {
// Navigate to markets page
await page.goto('/')
await page.click('a[href="/markets"]')
// Verify page loaded
await expect(page.locator('h1')).toContainText('Markets')
// Search for markets
await page.fill('input[placeholder="Search markets"]', 'election')
// Wait for debounce and results
await page.waitForTimeout(600)
// Verify search results displayed
const results = page.locator('[data-testid="market-card"]')
await expect(results).toHaveCount(5, { timeout: 5000 })
// Verify results contain search term
const firstResult = results.first()
await expect(firstResult).toContainText('election', { ignoreCase: true })
// Filter by status
await page.click('button:has-text("Active")')
// Verify filtered results
await expect(results).toHaveCount(3)
})
test('user can create a new market', async ({ page }) => {
// Login first
await page.goto('/creator-dashboard')
// Fill market creation form
await page.fill('input[name="name"]', 'Test Market')
await page.fill('textarea[name="description"]', 'Test description')
await page.fill('input[name="endDate"]', '2025-12-31')
// Submit form
await page.click('button[type="submit"]')
// Verify success message
await expect(page.locator('text=Market created successfully')).toBeVisible()
// Verify redirect to market page
await expect(page).toHaveURL(/\/markets\/test-market/)
})
```
## Test File Organization
```
src/
├── components/
│ ├── Button/
│ │ ├── Button.tsx
│ │ ├── Button.test.tsx # Unit tests
│ │ └── Button.stories.tsx # Storybook
│ └── MarketCard/
│ ├── MarketCard.tsx
│ └── MarketCard.test.tsx
├── app/
│ └── api/
│ └── markets/
│ ├── route.ts
│ └── route.test.ts # Integration tests
└── e2e/
├── markets.spec.ts # E2E tests
├── trading.spec.ts
└── auth.spec.ts
```
## Mocking External Services
### Supabase Mock
```typescript
jest.mock('@/lib/supabase', () => ({
supabase: {
from: jest.fn(() => ({
select: jest.fn(() => ({
eq: jest.fn(() => Promise.resolve({
data: [{ id: 1, name: 'Test Market' }],
error: null
}))
}))
}))
}
}))
```
### Redis Mock
```typescript
jest.mock('@/lib/redis', () => ({
searchMarketsByVector: jest.fn(() => Promise.resolve([
{ slug: 'test-market', similarity_score: 0.95 }
])),
checkRedisHealth: jest.fn(() => Promise.resolve({ connected: true }))
}))
```
### OpenAI Mock
```typescript
jest.mock('@/lib/openai', () => ({
generateEmbedding: jest.fn(() => Promise.resolve(
new Array(1536).fill(0.1) // Mock 1536-dim embedding
))
}))
```
## Test Coverage Verification
### Run Coverage Report
```bash
npm run test:coverage
```
### Coverage Thresholds
```json
{
"jest": {
"coverageThresholds": {
"global": {
"branches": 80,
"functions": 80,
"lines": 80,
"statements": 80
}
}
}
}
```
## Common Testing Mistakes to Avoid
### ❌ WRONG: Testing Implementation Details
```typescript
// Don't test internal state
expect(component.state.count).toBe(5)
```
### ✅ CORRECT: Test User-Visible Behavior
```typescript
// Test what users see
expect(screen.getByText('Count: 5')).toBeInTheDocument()
```
### ❌ WRONG: Brittle Selectors
```typescript
// Breaks easily
await page.click('.css-class-xyz')
```
### ✅ CORRECT: Semantic Selectors
```typescript
// Resilient to changes
await page.click('button:has-text("Submit")')
await page.click('[data-testid="submit-button"]')
```
### ❌ WRONG: No Test Isolation
```typescript
// Tests depend on each other
test('creates user', () => { /* ... */ })
test('updates same user', () => { /* depends on previous test */ })
```
### ✅ CORRECT: Independent Tests
```typescript
// Each test sets up its own data
test('creates user', () => {
const user = createTestUser()
// Test logic
})
test('updates user', () => {
const user = createTestUser()
// Update logic
})
```
## Continuous Testing
### Watch Mode During Development
```bash
npm test -- --watch
# Tests run automatically on file changes
```
### Pre-Commit Hook
```bash
# Runs before every commit
npm test && npm run lint
```
### CI/CD Integration
```yaml
# GitHub Actions
- name: Run Tests
run: npm test -- --coverage
- name: Upload Coverage
uses: codecov/codecov-action@v3
```
## Best Practices
1. **Write Tests First** - Always TDD
2. **One Assert Per Test** - Focus on single behavior
3. **Descriptive Test Names** - Explain what's tested
4. **Arrange-Act-Assert** - Clear test structure
5. **Mock External Dependencies** - Isolate unit tests
6. **Test Edge Cases** - Null, undefined, empty, large
7. **Test Error Paths** - Not just happy paths
8. **Keep Tests Fast** - Unit tests < 50ms each
9. **Clean Up After Tests** - No side effects
10. **Review Coverage Reports** - Identify gaps
## Success Metrics
- 80%+ code coverage achieved
- All tests passing (green)
- No skipped or disabled tests
- Fast test execution (< 30s for unit tests)
- E2E tests cover critical user flows
- Tests catch bugs before production
---
**Remember**: Tests are not optional. They are the safety net that enables confident refactoring, rapid development, and production reliability.

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---
name: verification-loop
description: >
A comprehensive verification system for Kiro sessions.
metadata:
origin: ECC
---
# Verification Loop Skill
A comprehensive verification system for Kiro sessions.
## When to Use
Invoke this skill:
- After completing a feature or significant code change
- Before creating a PR
- When you want to ensure quality gates pass
- After refactoring
## Verification Phases
### Phase 1: Build Verification
```bash
# Check if project builds
npm run build 2>&1 | tail -20
# OR
pnpm build 2>&1 | tail -20
```
If build fails, STOP and fix before continuing.
### Phase 2: Type Check
```bash
# TypeScript projects
npx tsc --noEmit 2>&1 | head -30
# Python projects
pyright . 2>&1 | head -30
```
Report all type errors. Fix critical ones before continuing.
### Phase 3: Lint Check
```bash
# JavaScript/TypeScript
npm run lint 2>&1 | head -30
# Python
ruff check . 2>&1 | head -30
```
### Phase 4: Test Suite
```bash
# Run tests with coverage
npm run test -- --coverage 2>&1 | tail -50
# Check coverage threshold
# Target: 80% minimum
```
Report:
- Total tests: X
- Passed: X
- Failed: X
- Coverage: X%
### Phase 5: Security Scan
```bash
# Check for secrets
grep -rn "sk-" --include="*.ts" --include="*.js" . 2>/dev/null | head -10
grep -rn "api_key" --include="*.ts" --include="*.js" . 2>/dev/null | head -10
# Check for console.log
grep -rn "console.log" --include="*.ts" --include="*.tsx" src/ 2>/dev/null | head -10
```
### Phase 6: Diff Review
```bash
# Show what changed
git diff --stat
git diff HEAD~1 --name-only
```
Review each changed file for:
- Unintended changes
- Missing error handling
- Potential edge cases
## Output Format
After running all phases, produce a verification report:
```
VERIFICATION REPORT
==================
Build: [PASS/FAIL]
Types: [PASS/FAIL] (X errors)
Lint: [PASS/FAIL] (X warnings)
Tests: [PASS/FAIL] (X/Y passed, Z% coverage)
Security: [PASS/FAIL] (X issues)
Diff: [X files changed]
Overall: [READY/NOT READY] for PR
Issues to Fix:
1. ...
2. ...
```
## Continuous Mode
For long sessions, run verification every 15 minutes or after major changes:
```markdown
Set a mental checkpoint:
- After completing each function
- After finishing a component
- Before moving to next task
Run: /verify
```
## Integration with Hooks
This skill complements postToolUse hooks but provides deeper verification.
Hooks catch issues immediately; this skill provides comprehensive review.