k6 Script Reference

Testlyn runs the official, unmodified grafana/k6 binary. Any valid k6 script runs here — we don't add extensions, we don't restrict the k6 API.

What's supported

Everything in stock k6:

• HTTP/1.1 and HTTP/2 (k6/http)
• WebSockets (k6/ws)
• gRPC (k6/net/grpc)
• Checks and thresholds
• Groups and tags
• Custom metrics
• Scenarios (ramping-vus, constant-arrival-rate, etc.)
• Environment variables via __ENV
• Shared iterations

Options reference

Common options you'll use:

export const options = {
  // Simple: fixed VUs for a duration
  vus: 50,
  duration: '2m',

  // Or: scenarios for more control
  scenarios: {
    ramp_up: {
      executor: 'ramping-vus',
      startVUs: 0,
      stages: [
        { duration: '1m', target: 100 },
        { duration: '3m', target: 100 },
        { duration: '1m', target: 0 },
      ],
    },
  },

  // Thresholds — test fails if not met
  thresholds: {
    http_req_duration: ['p(95)<500'],
    http_req_failed: ['rate<0.01'],
  },
};

Limits per tier

If your script exceeds the limit for your tier, the run is rejected before starting with a 402 Payment Required response.

What's not supported

• xk6 extensions — we run stock k6, no custom extensions. If your script uses an xk6 import, it will fail.
• Browser API — chromium.launch() is not supported in Phase 1.
• Local file system access — scripts cannot read files from disk. Inline your data or use __ENV for dynamic values.

Debugging tips

Set export const options = { vus: 1, duration: '10s' } when writing your script. Run locally first with docker run --rm -v $(pwd):/scripts grafana/k6 run /scripts/test.js. Once it passes locally, paste it into Testlyn.