k6-load-testing

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 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.