What Is Stresseur? The AI Test Engineer for APIs

Stresseur is the AI test engineer for APIs. It records how an API is really used during development, turns those flows into YAML tests, runs them in CI on every pull request, and shows which flow and which step got slower. It is a testing product for APIs. The sections below cover what it is, how the workflow runs, its two parts, and what its AI test engineer does and does not do.

What Stresseur is

Put plainly, Stresseur is a tool you point at your own API. It records real usage while you develop and turns those flows into YAML tests. Those tests run in CI on every pull request. Any recorded flow can also run as a load test.

The name is easy to confuse with the word “stressor”: searching “what is stresseur” puts a page about that word first. Stresseur has nothing to do with it. It is software for testing APIs, made by the DevTools team.

How Stresseur works

The workflow has four steps.

1. Install. In a project, run npm install -D stresseur stresseur-recorder. The recorder SDK runs in development only.
2. Record. Using the API in development produces flows. They live in the repository under api-tests/ as *.yamlflow.yaml files.
3. Run in CI. The workflow runs each flow 13 times, one warm-up and 12 measured, and uploads per-step timings. In GitHub Actions it authenticates with GitHub OIDC, so there is no token to store.
4. Read the result. A flow is flagged when its median is at least 10% slower than the baseline and outside its normal run-to-run variation. The baseline is the last 30 comparable runs on the default branch. Each pull request gets one check, “Stresseur / performance”, and one comment that is updated in place on each push.

Gates live in api-tests/stresseur.yml.

The CLI and Stresseur Cloud

Stresseur has two parts. The first is the open-source CLI and flow runner, the npm package stresseur, run as npx stresseur. It is free, works with or without a workspace, and runs on the open-source DevTools engine under the Apache-2.0 license.

The second is Stresseur Cloud, the web app at app.stresseur.com. It is live, with a Free plan and paid plans. Cloud load tests start load generators in the regions you pick, Frankfurt, Virginia, San Jose or Singapore, and stream results live: virtual users, requests per second, p95, errors and per-step latency.

The AI test engineer and its limits

To use the AI test engineer, tag @stresseur on a pull request or issue, or ask from the app.

Its limits are set on purpose. It never merges, never approves and never pushes to the default branch. Draft fix pull requests, the “@stresseur fix this” request, are built but sit behind a flag and are not on for customers, so they are not available today. Stresseur posts checks, comments and answers, and code changes stay with people. A person reads the check, the comment or the answer, and a person decides what to change.

Where to start

Stresseur is a testing product for APIs: it records real usage, keeps flows as YAML in your repository, measures them on every pull request and reports which step got slower. The CLI is free to try with npx stresseur, and the docs at /docs cover the quickstart and the CLI reference.