DocumentationGrafana k6Using k6Checks

Checks

Checks validate boolean conditions in your test. Testers often use checks to validate that the system is responding with the expected content. For example, a check could validate that a POST request has a response.status == 201, or that the body is of a certain size.

Checks are similar to what many testing frameworks call an assert, but failed checks do not cause the test to abort or finish with a failed status. Instead, k6 keeps track of the rate of failed checks as the test continues to run

Each check creates a rate metric . To make a check abort or fail a test, you can combine it with a Threshold .

Check for HTTP response code

Checks are great for codifying assertions relating to HTTP requests and responses. For example, this snippet makes sure the HTTP response code is a 200:

JavaScript

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

export default function () {
  const res = http.get('http://test.k6.io/');
  check(res, {
    'is status 200': (r) => r.status === 200,
  });
}

Check for text in response body

Sometimes, even an HTTP 200 response contains an error message. In these situations, consider adding a check to verify the response body, like this:

JavaScript

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

export default function () {
  const res = http.get('http://test.k6.io/');
  check(res, {
    'verify homepage text': (r) =>
      r.body.includes('Collection of simple web-pages suitable for load testing'),
  });
}

Check for response body size

To verify the size of the response body, you can use a check like this:

JavaScript

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

export default function () {
  const res = http.get('http://test.k6.io/');
  check(res, {
    'body size is 11,105 bytes': (r) => r.body.length == 11105,
  });
}

See percentage of checks that passed

When a script includes checks, the summary report shows how many of the tests’ checks passed:

bash

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$ k6 run script.js

  ...
    ✓ is status 200

  ...
  checks.........................: 100.00% ✓ 1        ✗ 0
  data_received..................: 11 kB   12 kB/s

In this example, note that the check “is status 200” succeeded 100% of the times it was called.

Add multiple checks

You can also add multiple checks within a single check() statement:

JavaScript

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

export default function () {
  const res = http.get('http://test.k6.io/');
  check(res, {
    'is status 200': (r) => r.status === 200,
    'body size is 11,105 bytes': (r) => r.body.length == 11105,
  });
}

When this test executes, the output will look something like this:

bash

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$ k6 run checks.js

  ...
    ✓ is status 200
    ✓ body size is 11,105 bytes

  ...
  checks.........................: 100.00% ✓ 2        ✗ 0
  data_received..................: 11 kB   20 kB/s

Read more

• Check Javascript API
• Failing a load test using checks
• k6chaijs : use BDD assertions in k6