📚 Full Guide: Install & Use k6 for REST API Load Testing

---

1. What is k6?

k6 is an open-source load testing tool built in Go, designed for testing the performance of APIs, microservices, and websites.

---

Installation

Windows (using winget)

Open PowerShell or Command Prompt and run:

winget install k6

---

macOS (using Homebrew)

brew install k6

---

Linux (using apt for Debian/Ubuntu)

sudo apt update
sudo apt install -y gnupg software-properties-common
wget -q -O - https://dl.k6.io/key.gpg | sudo apt-key add -
echo "deb https://dl.k6.io/deb stable main" | sudo tee /etc/apt/sources.list.d/k6.list
sudo apt update
sudo apt install k6

---

Verify Installation

Run:

k6 version

You should see the installed k6 version printed.

---

Configuration

Create a test script file, for example course-load-test.js:

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

export const options = {
  vus: 100,
  duration: '30s',
  thresholds: {
    http_req_duration: ['p(95)<1000'],
    http_req_failed: ['rate<0.01'],
  },
};

const BASE_URL = 'http://localhost:8080/api/v1';

export default function () {
  let res = http.get(`${BASE_URL}/courses`);
  check(res, { 'GET /courses - status 200': (r) => r.status === 200 });

  res = http.get(`${BASE_URL}/courses/1`);
  check(res, { 'GET /courses/1 - status 200': (r) => r.status === 200 });

  res = http.post(`${BASE_URL}/courses`, JSON.stringify({
    name: `Course ${Math.random().toString(36).substring(2, 6)}`,
    duration: Math.floor(Math.random() * 10) + 1,
  }), { headers: { 'Content-Type': 'application/json' } });
  check(res, { 'POST /courses - status 200': (r) => r.status === 200 });
}

---

Running the Test

Run the test with:

k6 run course-load-test.js

---

Useful k6 Commands

• Run a script:

  k6 run script.js

• Show k6 help:

  k6 --help

• Run test with 50 virtual users for 1 minute:

  k6 run --vus 50 --duration 1m script.js

• Output results to JSON:

  k6 run --out json=output.json script.js

---

That’s it! You now have k6 installed and can run your load tests.

If you want me to include extra tips or examples, just ask!