Grafana k6 Has a Free Load Testing Tool — Write Performance Tests in JavaScript Not XML

Why k6?

k6 is a modern load testing tool that uses JavaScript instead of JMeter's XML. Built in Go for performance, runs locally.

Quick Start

brew install k6

import http from "k6/http"
import { check, sleep } from "k6"

export const options = {
  vus: 50,
  duration: "30s",
}

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

Ramping Scenarios

export const options = {
  stages: [
    { duration: "2m", target: 100 },
    { duration: "5m", target: 100 },
    { duration: "2m", target: 200 },
    { duration: "5m", target: 200 },
    { duration: "2m", target: 0 },
  ],
  thresholds: {
    http_req_duration: ["p(95)<500"],
    http_req_failed: ["rate<0.01"],
  },
}

API Testing with Auth

export function setup() {
  const res = http.post("https://api.example.com/auth/login",
    JSON.stringify({ email: "[e-mail]", password: "pass" }),
    { headers: { "Content-Type": "application/json" } }
  )
  return { token: res.json("token") }
}

export default function (data) {
  const headers = { Authorization: "Bearer " + data.token }
  const res = http.get("https://api.example.com/users", { headers })
  check(res, { "200 OK": (r) => r.status === 200 })
}

k6 vs Alternatives

Feature	k6	JMeter	Gatling
Language	JavaScript	XML/GUI	Scala
Engine	Go	Java	Scala
Resources	Low	High	Medium
CI/CD	Easy	Complex	Medium

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