---
title: "Add checks to your script | Grafana Labs"
description: "Use the k6 check() API to validate response status codes and body content alongside performance metrics."
---

# Add checks to your script

A fast response isn’t useful if it returns an error. Checks let you validate that responses are correct, not just quick, by asserting conditions on every response. Unlike traditional test assertions, a failed check doesn’t stop the test. Instead, k6 tracks the pass rate so you can see how often correctness degrades under load.

This is a critical step that many new users skip. Without checks, your baseline only measures speed. With checks, it also measures correctness, giving you a complete picture of system health.

To add checks to your baseline script, complete the following steps:

1. Open `baseline.js` and update the import statement to include `check`:
   
   JavaScript ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy
   
   ```javascript
   import http from 'k6/http';
   import { check, sleep } from 'k6';
   ```
2. In the default function, assign the HTTP response to a variable and add checks after the request:
   
   JavaScript ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy
   
   ```javascript
   export default function () {
     const res = http.get('https://quickpizza.grafana.com');
   
     check(res, {
       'status is 200': (r) => r.status === 200,
       'response body is not empty': (r) => r.body.length > 0,
     });
   
     sleep(1);
   }
   ```
   
   Each check has a descriptive name and a function that returns `true` or `false`. You can add as many checks as you need. Common checks include status codes, response body content, and response headers.
3. Save the file. Your complete `baseline.js` should now look like this:
   
   JavaScript ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy
   
   ```javascript
   import http from 'k6/http';
   import { check, sleep } from 'k6';
   
   export const options = {
     stages: [
       { duration: '30s', target: 20 },
       { duration: '1m', target: 20 },
       { duration: '30s', target: 0 },
     ],
   };
   
   export default function () {
     const res = http.get('https://quickpizza.grafana.com');
   
     check(res, {
       'status is 200': (r) => r.status === 200,
       'response body is not empty': (r) => r.body.length > 0,
     });
   
     sleep(1);
   }
   ```
   
   When you run this test, the summary output includes a `checks` line showing the total pass rate across all check assertions.

In the next milestone, you run this test and learn how to read the results.