english/.opencode/skills/web-testing/references/load-testing-k6.md

Load Testing with k6

Installation

brew install k6          # macOS
winget install k6        # Windows
docker run -i grafana/k6 run - <script.js

Basic Load Test

import http from 'k6/http';
import { check, sleep } from 'k6';

export const options = {
  vus: 10,
  duration: '30s',
};

export default function () {
  const res = http.get('http://localhost:3000/api/users');
  check(res, {
    'status is 200': (r) => r.status === 200,
    'response < 500ms': (r) => r.timings.duration < 500,
  });
  sleep(1);
}

Stress Test with Stages

export const options = {
  stages: [
    { duration: '2m', target: 50 },
    { duration: '5m', target: 50 },
    { duration: '2m', target: 100 },
    { duration: '2m', target: 0 },
  ],
  thresholds: {
    http_req_duration: ['p(95)<500'],
    http_req_failed: ['rate<0.01'],
  },
};

With Authentication

export function setup() {
  const res = http.post(`${BASE_URL}/api/login`, {
    email: 'test@example.com', password: 'password',
  });
  return { token: res.json('token') };
}

export default function (data) {
  const params = { headers: { Authorization: `Bearer ${data.token}` } };
  http.get(`${BASE_URL}/api/protected`, params);
}

Performance Thresholds

Metric	Good	Warning
p50 latency	<200ms	<500ms
p95 latency	<500ms	<1s
Error rate	<0.1%	<1%

Commands

k6 run script.js
k6 run --out json=results.json script.js
k6 cloud script.js  # Grafana Cloud

Artillery Alternative

config:
  target: 'http://localhost:3000'
  phases: [{ duration: 60, arrivalRate: 10 }]
scenarios:
  - flow: [{ get: { url: '/api/users' } }]

npx artillery run artillery.yml