Lab: First k6 test with checks and thresholds

What you will learn in this TP

• Write a k6 script
• Add checks and thresholds
• Interpret the summary

Introduction #

What you will learn in this section

• Write a k6 script
• Add checks and thresholds
• Interpret the summary

Context. An API is about to be exposed to a new partner. Before opening access, you check that it handles a modest load with acceptable latency.

Prerequisites: Docker  ·  Estimated time: 30 min

Your first automatable load test.

Hands-on #

Guided steps, with their solutions.

1. 1. Start the target API

   Why? httpbin provides predictable routes: normal, slow or error responses on demand.

   Run httpbin in a dedicated Docker network.

2. 2. Write the script

   Why? A minimal test: 10 VUs for 30 s on a simple route.

   Create smoke.js that calls http://httpbin/get with a check on the status.

3. 3. Add thresholds

   Why? Thresholds turn a measurement into a verdict: the test fails if the objective is not met.

   Add the thresholds: fewer than 1% failures, p95 under 200 ms. Run it again and note the exit code.

4. 4. Make the test fail

   Why? Checking that a test can fail is as important as seeing it pass.

   Replace the route with /delay/1 (1 s response). What happens?

5. 5. Read the summary

   Why? Knowing how to read each line avoids hasty conclusions.

   Note down http_reqs, http_req_duration (avg, p95), iterations and checks. Why is the throughput around 10 requests per second?

Difficulty level : ●○○○○ (1/5)