Documentation Grafana k6 JavaScript API k6 check( val, sets, [tags] )

check( val, sets, [tags] )

Run checks on a value. A check is a test condition that can give a truthy or falsy result. The sets parameter contains one or more checks, and the check() function will return false if any of them fail.

Note that checks are not asserts in their traditional sense - a failed assertion will throw an error, while a check will always return with a pass or a failure. Failure conditions can then instead be controlled by thresholds, for more power and flexibility.

Returns

Examples

Using check() to verify that an HTTP response code was 200:

JavaScript

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JavaScript Copy

import http from 'k6/http';
import { check } from 'k6';

export default function () {
  const res = http.get('https://quickpizza.grafana.com/');
  check(res, {
    'response code was 200': (res) => res.status == 200,
  });
}

Using check() with a custom tag to verify that an HTTP response code was 200 and that body was 1234 bytes. The checkOutput can be used for any condition in your script logic:

JavaScript

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JavaScript Copy

import http from 'k6/http';
import { check, fail } from 'k6';

export default function () {
  const res = http.get('https://quickpizza.grafana.com/');
  const checkOutput = check(
    res,
    {
      'response code was 200': (res) => res.status == 200,
      'body size was larger than 123 bytes': (res) => res.body.length > 123,
    },
    { myTag: "I'm a tag" }
  );

  if (!checkOutput) {
    fail('unexpected response');
  }
}