k6 Load Test Script Generator

k6 is an open-source load testing tool by Grafana. You write test scripts in JavaScript and run them from the CLI. It supports ramp-up stages, thresholds for pass/fail criteria, and detailed metrics like response time percentiles, RPS, and error rates. Unlike browser-based tools, k6 generates high concurrency from a single machine and integrates well with CI/CD pipelines.

Virtual Users (VUs) are concurrent simulated users sending requests to your server. 50 VUs means 50 requests are in flight simultaneously. VUs execute your test script in a loop — each iteration makes the HTTP request, sleeps, and repeats. The number of iterations per second depends on response time and the sleep duration.

Stages define a ramp-up/ramp-down pattern for VUs over time. A typical pattern: ramp from 0 to 50 VUs over 30s, hold at 50 VUs for 1 minute, then ramp down to 0 over 30s. This simulates gradual user arrival and departure, avoids cold-start spikes, and gives your system time to warm up.

Thresholds are pass/fail criteria for your load test. Common ones: http_req_duration p(95) < 500ms (95th percentile response time under 500ms) and http_req_failed rate < 0.01 (less than 1% error rate). If any threshold is breached, k6 exits with a non-zero status code — perfect for failing CI pipelines.

For Bearer token auth, add 'Authorization': 'Bearer YOUR_TOKEN' to the headers object. For basic auth, use btoa() to encode credentials. For session-based auth, you can do a login request at the start of the test function and reuse the returned cookie. Use __ENV.TOKEN to inject secrets from environment variables without hardcoding them in the script.

Yes. k6 runs headlessly with no browser required. In GitHub Actions: add a step with 'uses: grafana/setup-k6-action@v1' then 'run: k6 run load-test.js'. k6 exits non-zero when thresholds fail, which fails the CI step. Grafana Cloud k6 can run distributed tests and store historical results.