Reuse and re-run tests

In the previous tutorials, you designed k6 scripts to assert performance and make comparing results easy.

In this tutorial, learn how to:

Modularize test scripts into reusable components
Dynamically configure scripts with environment variables

Example script

For fun, let’s combine the scripts from the previous tutorials. Use the logic of the multiple-flows.js test with the thresholds and scenario of the api-test.js (feel free to add more checks, requests, groups, and so on). Take note of the features of this script:

The default function has two groups, Contacts flow, and Coinflip game
The options object has two properties, thresholds and scenarios

In the following sections, learn how to split these components into separate files, and combine them dynamically at run time.

import http from 'k6/http';
import { group, sleep } from 'k6';
import { Trend } from 'k6/metrics';

//define configuration
export const options = {
  scenarios: {
    //arbitrary name of scenario:
    breaking: {
      executor: 'ramping-vus',
      stages: [
        { duration: '10s', target: 20 },
        { duration: '50s', target: 20 },
        { duration: '50s', target: 40 },
        { duration: '50s', target: 60 },
        { duration: '50s', target: 80 },
        { duration: '50s', target: 100 },
        { duration: '50s', target: 120 },
        { duration: '50s', target: 140 },
        //....
      ],
    },
  },
  //define thresholds
  thresholds: {
    http_req_failed: [{ threshold: 'rate<0.01', abortOnFail: true }], // availability threshold for error rate
    http_req_duration: ['p(99)<1000'], // Latency threshold for percentile
  },
};

//set baseURL
const baseUrl = 'https://test.k6.io';

// Create custom trends
const contactsLatency = new Trend('contacts_duration');
const coinflipLatency = new Trend('coinflip_duration');

export default function () {
  // Put visits to contact page in one group
  let res;
  group('Contacts flow', function () {
    // save response as variable
    res = http.get(`${baseUrl}/contacts.php`);
    // add duration property to metric
    contactsLatency.add(res.timings.duration);
    sleep(1);

    res = http.get(`${baseUrl}/`);
    // add duration property to metric
    contactsLatency.add(res.timings.duration);
    sleep(1);
  });

  // Coinflip players in another group

  group('Coinflip game', function () {
    // save response as variable
    let res = http.get(`${baseUrl}/flip_coin.php?bet=heads`);
    // add duration property to metric
    coinflipLatency.add(res.timings.duration);
    sleep(1);

    res = http.get(`${baseUrl}/flip_coin.php?bet=tails`);
    // add duration property to metric
    coinflipLatency.add(res.timings.duration);
    sleep(1);
  });
}

Modularize logic

With modules, you can use logic and variables from other files. Use modules to extract the functions to their own files.

To do so, follow these steps:

Copy the previous script (whole-tutorial.js) and save it as main.js.

Extract the Contacts flow group function from main.js script file and paste it into a new file called contacts.js

export function contacts() {
  group('Contacts flow', function () {
    // save response as variable
    let res = http.get(`${baseUrl}/contacts.php`);
    // add duration property to metric
    contactsLatency.add(res.timings.duration);
    sleep(1);

    res = http.get(`${baseUrl}/`);
    // add duration property to metric
    contactsLatency.add(res.timings.duration);
    sleep(1);
  });
}

As is, this script won’t work, since it has undeclared functions and variables.

Add the necessary imports and variables. This script uses the group, sleep, and http functions or libraries. It also has a custom metric. Since this metric is specific to the group, you can add it contacts.js.

Finally, pass baseUrl as a parameter of the contacts function.

import http from 'k6/http';
import { Trend } from 'k6/metrics';
import { group, sleep } from 'k6';

const contactsLatency = new Trend('contact_duration');

export function contacts(baseUrl) {
  group('Contacts flow', function () {
    // save response as variable
    let res = http.get(`${baseUrl}/contacts.php`);
    // add duration property to metric
    contactsLatency.add(res.timings.duration);
    sleep(1);

    res = http.get(`${baseUrl}/`);
    // add duration property to metric
    contactsLatency.add(res.timings.duration);
    sleep(1);
  });
}

Repeat the process with the coinflip group in a file called coinflip.js. Use the tabs to see the final three files should (options moved to the bottom of main.js for better readability).

import { contacts } from './contacts.js';
import { coinflip } from './coinflip.js';

const baseUrl = 'https://test.k6.io';

export default function () {
  // Put visits to contact page in one group
  contacts(baseUrl);
  // Coinflip players in another group
  coinflip(baseUrl);
}

//define configuration
export const options = {
  scenarios: {
    //arbitrary name of scenario:
    breaking: {
      executor: 'ramping-vus',
      stages: [
        { duration: '10s', target: 20 },
        { duration: '50s', target: 20 },
        { duration: '50s', target: 40 },
        { duration: '50s', target: 60 },
        { duration: '50s', target: 80 },
        { duration: '50s', target: 100 },
        { duration: '50s', target: 120 },
        { duration: '50s', target: 140 },
        //....
      ],
    },
  },
  //define thresholds
  thresholds: {
    http_req_failed: [{ threshold: 'rate<0.01', abortOnFail: true }], // availability threshold for error rate
    http_req_duration: ['p(99)<1000'], // Latency threshold for percentile
  },
};

import http from 'k6/http';
import { Trend } from 'k6/metrics';
import { group, sleep } from 'k6';

const contactsLatency = new Trend('contact_duration');

export function contacts(baseUrl) {
  group('Contacts flow', function () {
    // save response as variable
    let res = http.get(`${baseUrl}/contacts.php`);
    // add duration property to metric
    contactsLatency.add(res.timings.duration);
    sleep(1);

    res = http.get(`${baseUrl}/`);
    // add duration property to metric
    contactsLatency.add(res.timings.duration);
    sleep(1);
  });
}

import http from 'k6/http';
import { Trend } from 'k6/metrics';
import { group, sleep } from 'k6';

const coinflipLatency = new Trend('coinflip_duration');

export function coinflip(baseUrl) {
  group('Coinflip game', function () {
    // save response as variable
    let res = http.get(`${baseUrl}/flip_coin.php?bet=heads`);
    // add duration property to metric
    coinflipLatency.add(res.timings.duration);
    sleep(1);
    // mutate for new request
    res = http.get(`${baseUrl}/flip_coin.php?bet=tails`);
    // add duration property to metric
    coinflipLatency.add(res.timings.duration);
    sleep(1);
  });
}

Run the test:

# setting the workload to 10 iterations to limit run time
k6 run main.js --iterations 10

The results should be very similar to running the script in a combined file, since these are the same test.

Modularize workload

Now that the iteration code is totally modularized, you might modularize your options, too.

The following example creates a module config.js to export the threshold and workload settings.

import { coinflip } from './coinflip.js';
import { contacts } from './contacts.js';
import { thresholdsSettings, breakingWorkload } from './config.js';

export const options = {
  scenarios: { breaking: breakingWorkload },
  thresholds: thresholdsSettings,
};

const baseUrl = 'https://test.k6.io';

export default function () {
  contacts(baseUrl);
  coinflip(baseUrl);
}

export const thresholdsSettings = {
  http_req_failed: [{ threshold: 'rate<0.01', abortOnFail: true }],
  http_req_duration: ['p(99)<1000'],
};

export const breakingWorkload = {
  executor: 'ramping-vus',
  stages: [
    { duration: '10s', target: 20 },
    { duration: '50s', target: 20 },
    { duration: '50s', target: 40 },
    { duration: '50s', target: 60 },
    { duration: '50s', target: 80 },
    { duration: '50s', target: 100 },
    { duration: '50s', target: 120 },
    { duration: '50s', target: 140 },
    //....
  ],
};

Notice the length of this final script and compare it with the script at the beginning of this page. Though the final execution is the same, it’s half the size and more readable.

Besides shortness, this modularity lets you compose scripts from many parts, or dynamically configure scripts at run time.

Mix and match logic

With modularized configuration and logic, you can mix and match logic. An easy way to configure this is through environment variables.

Change main.js and config.js so that it:

By default runs a smoke test with 5 iterations
With the right environment variable value, runs a breaking test

To do this, follow these steps:

Add the workload settings for configuring the smoke test to config.js:

export const smokeWorkload = {
  executor: 'shared-iterations',
  iterations: 5,
  vus: 1,
};

export const thresholdsSettings = {
  http_req_failed: [{ threshold: 'rate<0.01', abortOnFail: true }],
  http_req_duration: ['p(99)<1000'],
};

export const breakingWorkload = {
  executor: 'ramping-vus',
  stages: [
    { duration: '10s', target: 20 },
    { duration: '50s', target: 20 },
    { duration: '50s', target: 40 },
    { duration: '50s', target: 60 },
    { duration: '50s', target: 80 },
    { duration: '50s', target: 100 },
    { duration: '50s', target: 120 },
    { duration: '50s', target: 140 },
    //....
  ],
};

Edit main.js to choose the workload settings depending on the WORKLOAD environment variable. For example:

import { coinflip } from './coinflip.js';
import { contacts } from './contacts.js';
import { thresholdsSettings, breakingWorkload, smokeWorkload } from './config.js';

export const options = {
  scenarios: {
    my_scenario: __ENV.WORKLOAD === 'breaking' ? breakingWorkload : smokeWorkload,
  },
  thresholds: thresholdsSettings,
};

const baseUrl = 'https://test.k6.io';

export default function () {
  contacts(baseUrl);
  coinflip(baseUrl);
}

Run the script with and without the -e flag.
- What happens when you run k6 run main.js?
- What about k6 run main.js -e WORKLOAD=breaking?

This was a simple example to showcase how you can modularize a test. As your test suite grows and more people are involved in performance testing, your modularization strategy becomes essential to building and maintaining an efficient testing suite.

Next steps

Now you’ve seen examples to write tests, assert for performance, filter results, and modularize scripts. Notice how the tests progress in complexity: from single endpoints to holistic tests, from small to large loads, and from single tests to reusable modules. These progressions are typical in testing, with the next step being to automate. It might be impractical to automate a tutorial, but if you are interested, read the Automated performance testing guide.

More likely, you want to learn more about k6. The k6-learn repository has more details to practice. Or, you can read and explore the testing guides and try to build out your testing strategy.

Happy testing!