Documentation Grafana k6 Examples Get started with k6 Test for functional behavior

Test for functional behavior

In this tutorial, learn how to write a test that does the following:

• Sends a POST request to the new endpoint
• Creates a check for the response status

Script the Request

The first thing to do is to add logic for the endpoint. To do that, you need to make an HTTP request:

1. Import the HTTP module.
2. Create a payload to authenticate the user.
3. Use the http.post method to send your request with the payload to an endpoint.

To test, copy this file and save it as api-test.js.

JavaScript

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// import necessary module
import http from 'k6/http';

export default function () {
  // define URL and payload
  const url = 'https://test-api.k6.io/auth/basic/login/';
  const payload = JSON.stringify({
    username: 'test_case',
    password: '1234',
  });

  const params = {
    headers: {
      'Content-Type': 'application/json',
    },
  };

  // send a post request and save response as a variable
  const res = http.post(url, payload, params);
}

Run the script using the k6 run command:

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k6 run api-test.js

After the test finishes, k6 reports the default result summary.

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          /\      |‾‾| /‾‾/   /‾‾/
     /\  /  \     |  |/  /   /  /
    /  \/    \    |     (   /   ‾‾\
   /          \   |  |\  \ |  (‾)  |
  / __________ \  |__| \__\ \_____/ .io

  execution: local
     script: api-test.js
     output: -
  ...

As an optional step, you can log the response body to the console to make sure you’re getting the right response.

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export default function () {
  // ...

  const res = http.post(url, payload, params);

  // Log the request body
  console.log(res.body);
}

Add response checks

Once you’re sure the request is well-formed, add a check that validates whether the system responds with the expected status code.

1. Update your script so it has the following check function.

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// Import necessary modules
import { check } from 'k6';
import http from 'k6/http';

export default function () {
  // define URL and request body
  const url = 'https://test-api.k6.io/auth/basic/login/';
  const payload = JSON.stringify({
    username: 'test_case',
    password: '1234',
  });
  const params = {
    headers: {
      'Content-Type': 'application/json',
    },
  };

  // send a post request and save response as a variable
  const res = http.post(url, payload, params);

  // check that response is 200
  check(res, {
    'response code was 200': (res) => res.status == 200,
  });
}

1. Run the script again.

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k6 run api-test.js

1. Inspect the result output for your check. It should look something like this.

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   ✓ response code was 200

Next steps

In this tutorial, you’ve used k6 to make a POST request and check that it responds with a 200 status.

However, these tests make only one request, which doesn’t say much about how the system will respond under load. For that, you need to test under load.