Introduction

K6 is an open-source tool designed for performance and load testing. It is written in Go and provides an easy way to write tests using JavaScript. K6 can be used for both API testing and load testing.

Installation

To use K6, the CLI must be installed. Grafana has created a guide that describes the process on different operating systems. An easy way is to download the latest GitHub release of K6 and move the executable to the correct location.

  wget https://github.com/grafana/k6/releases/download/v0.53.0/k6-v0.53.0-linux-amd64.tar.gz
tar -xvf k6-v0.53.0-linux-amd64.tar.gz
sudo mv k6-v0.53.0-linux-amd64/k6 /usr/local/bin/

Developing

Load and performance tests for K6 are written in JavaScript and use the k6 API. Here is a simple example:

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

export const options = {
  // Stages with number of virtual users and duration
  stages: [
    { duration: '30s', target: 20 },
    { duration: '1m', target: 10 },
    { duration: '30s', target: 0 }
  ],

  thresholds: {
    http_req_failed: ['rate<0.01'], // less than 1% of requests should fail
    http_req_duration: ['p(95)<500'], // 95% of requests should be under 500ms
  },
}

// Test function
export default function() {
  // Execute request
  const res = http.get('https://example.com');

  // Check result
  check(res, {
    'status is 200': (r) => r.status === 200,
  });
  sleep(0.1);
}

Testing

A test can then be executed with the run command of k6, specifying the JavaScript file as a parameter. For example, k6 run test.js. This will start the test, which may take some time. Once the test is finished, K6 will display a summary of the test with all metrics. This might look like this:

K6 Test Result
Running the K6 test in the terminal

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Last updated 08 Jan 2025, 17:05 +0100 . history