k6-load-testing – Coding skill for AI agents

k6 Load Testing

Execution scope

Confirm exact target, environment, VU/request-rate/duration ceilings, window, stop conditions, downstream effects and test-data cleanup before load. Start at one VU; examples are not permission to stress a public endpoint. Cloud output requires authorization to upload results and incur charges. Checks alone do not fail a k6 run: add checks thresholds for asserted functional correctness. Fixtures must be nonempty and user allocation must match concurrency; modulo reuse can distort auth results.

Detailed Guide

Read [the detailed guide](references/detailed-guide.md) before executing this skill. It retains the complete procedure and reference material. Treat its safety, prerequisites, and validation requirements as mandatory. For focused work, load the relevant sections; for end-to-end work, read the guide completely.

When to Use This Skill

• Use when you need to load test HTTP APIs, WebSocket endpoints, or browser scenarios
• Use when setting up performance regression tests in CI/CD
• Use when analyzing system behavior under various load conditions
• Use when comparing performance between code changes
• Use when validating SLA requirements and performance budgets

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Examples

Example 1: Basic API Load Test

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

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

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

Example 2: Test with Authentication and Data Parameterization

import http from 'k6/http';
import { check } from 'k6';
import { SharedArray } from 'k6/data';

const users = new SharedArray('users', function () {
  return JSON.parse(open('./users.json'));
});

export default function () {
  const user = users[__VU % users.length];
  
  const loginRes = http.post('https://api.example.com/login',
    JSON.stringify({ email: user.email, password: user.password }),
    {headers: {'Content-Type': 'application/json'}, timeout: '10s', redirects: 0}
  );
  
  if (!check(loginRes, {'login succeeded': r => r.status === 200})) return;
  let token;
  try { token = loginRes.json('access_token'); } catch (_) { return; }
  if (typeof token !== 'string' || !token) return;
  
  const headers = { 'Authorization': `Bearer ${token}` };
  const res = http.get('https://api.example.com/profile', { headers });
  
  check(res, { 'profile loaded': (r) => r.status === 200 });
}

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Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.