Ramp Load with k6 Stages Profile
Define a k6 stage profile that ramps from 10 to 500 virtual users over 5 minutes so the breaking point is visible in the metrics.
Task
Add k6 run --env STAGES='10s:10,3m:500,1m:0' load.js to the test suite so regressions are caught automatically on every pull request.
When to use this
A refactor passes existing tests but breaks k6 run --env STAGES='10s:10,3m:500,1m:0' load.js, shipping a silent regression to users.
Prerequisites
- A test runner configured (Vitest or Jest)
- Source code with testable units
Steps
1. Configure k6 run --env STAGES='10s:10,3m:500,1m:0' load.js in the project configuration file with the recommended defaults.
k6 run --env STAGES='10s:10,3m:500,1m:0' load.js
Expected output: The configuration is accepted and k6 run --env STAGES='10s:10,3m:500,1m:0' load.js runs without errors on the first invocation.
2. Run the check locally to verify k6 run --env STAGES='10s:10,3m:500,1m:0' load.js produces the expected result before pushing.
pnpm test
Expected output: Local run matches CI behavior; no surprises after push.
3. Add the gate to the CI pipeline so k6 run --env STAGES='10s:10,3m:500,1m:0' load.js blocks merge on failure.
- name: Run add load test k6 ramp
run: pnpm test
Expected output: Pull requests with failing k6 run --env STAGES='10s:10,3m:500,1m:0' load.js are blocked from merging.
Troubleshooting
Problem
The check passes locally but fails in CI
Solution
Pin dependency versions and the runtime to match CI exactly; reproduce with the same Docker image or act.
Problem
Configuration is rejected with a schema error
Solution
Check the tool version matches the config schema; older versions may not support newer fields.
Limitations
- The gate only runs on events that trigger the workflow; locally pushed commits bypass it.
- Configuration drift is possible if someone edits settings outside version control.
Cover the regression path
Start by measuring the problem. Define a k6 stage profile that ramps from 10 to 500 virtual users over 5 minutes so the breaking point is visible in the metrics. The most common mistake is adding the gate without first confirming it catches the issue you care about. Run k6 run –env STAGES=‘10s:10,3m:500,1m:0’ load.js against the current codebase and inspect the output before wiring it into CI.
k6 run --env STAGES='10s:10,3m:500,1m:0' load.jsKeep tests maintainable
Once the gate is in place, make failures actionable. A failing k6 run –env STAGES=‘10s:10,3m:500,1m:0’ load.js should point to the exact file and line, not a generic error. Pin the tool version in the lockfile so a upstream release does not silently change behavior. Review the gate output in every pull request just like a test result.