Dockerized e2e tests


In my free time, I’m trying to learn something new and best of way learning is by doing. To avoid spinning my wheels in vain I’m helping to develop some product. In the previous post, I’ve described what we’ve decided to use for the UI and pointed out that I’m going to write integration tests. Here is how I integrated selenium e2e tests with gitlab-ci/travis-ci/whatever by running them in docker.

I don’t like either writing nor maintaining end to end tests and because of this, my approach is to write as little as possible of those. One might want to ask why do you write them at all? Well, the reason is that I’m aiming for continuous delivery and I’d prefer to know if a bunch of services I’m going to write will work together just fine. We are not creating another google where we can do canary release and do the tests on production because our potential 3 users might not be so happy about it :) That is why I’d like to write e2e tests which will cover critical functionalities of the system.

I’m aware that e2e tests don’t have good press and people don’t like them. I’m not going to create ice cream cone and I’d like to have feedback as fast as possible.

The Pug

I’m not making my living by writing tests but from I’ve heard selenium is still the best tool for the job and I’ve started with it. Then I’ve stumbled upon and it looks pretty good at first glance. Now when my basics were covered it was time to work on fast feedback loop and integrate it into our CI tool.

For the purpose of this post, I’ve ported this to travis-ci and it shouldn’t be a problem to implement using different CI tools (for example jenkins or whatever).

First things first. We are living in the containers era now and my first step was to see what I can find on I’ve found some useful stuff which saved me a lot of time: selenium/hub, selenium/node-chrome, selenium/node-firefox. With those containers, all of the heavy lifting is already done ;) and I was able to focus on putting it all to work.

For the purposes of this blog post, I’m going to write few tests for famous todo MVC app

I’ve started with wdio setup:

./node_modules/.bin/wdio config

And then just answered few questions. After few bad experiences, I’ve decided to pimp this configuration a bit and add something to do screenshots of the failed test:

afterTest: function (test) {
  if (test.passed) {


  const filename = encodeURIComponent(test.title.replace(/\s+/g, '-'));
  const filePath = this.screenshotPath + filename + '.png';


Next, I’ve written my first Page Object and 3 tests to have something to work with:

const itemSelector = index => `.todo-list li:nth-child(${index + 1})`;

class TodoPage {
  open() {
      () => browser.isVisible('.new-todo'),

  addNewItem(todo) {
    browser.setValue('.new-todo', `${todo}\uE006`);

  gettodoText(index) {
    return $(itemSelector(index)).getText();

  get itemsCount() {
    if (!($('.todo-list').isVisible())) {
      return 0;

    return browser.elements('.todo-list li').value.length;

  get itemsCounterValue() {
    return parseInt($('.todo-count strong').getText(), 10);

  get title() {
    return browser.getTitle();

export default new TodoPage();
import { expect } from 'chai';
import todoPage from './';

describe('spec1', () => {
  it('should open todo app main page', () => {
    // when;

    // then
    expect(todoPage.title).to.equal('React • TodoMVC');
import { expect } from 'chai';
import todoPage from './';

describe('spec2', () => {
  beforeEach(() => {;

  it('should add new item to list', () => {
    // given
    const todoItemText = 'new item';

    // when

    // then

  it('should display valid items count', () => {
    // when

    // then

I’ve split tests intentionally for the purposes of the demo. When running tests from multiple files wdio will create up to maxInstances of each browser which should speed up the testing process..

The last step was to dockerize todo application (in real life example I was running those tests after deployment on ECS was finished, as a part of the continuous delivery pipeline) - Dockerfile.

For easier local development I’ve created docker-compose which allows me to boot up application, selenium and browsers in docker, and run the tests from host machine:

version: '3'

    image: selenium/hub:3.8.1
      - 4444:4444

    image: selenium/node-chrome:3.8.1
      - selenium
      - /dev/shm:/dev/shm
      - HUB_HOST=selenium
      - HUB_PORT=4444

    image: selenium/node-firefox:3.8.1
      - selenium
      - /dev/shm:/dev/shm
    - HUB_HOST=selenium
    - HUB_PORT=4444

    build: app/
      - 8080:80

    build: .
      - selenium
      - chrome
      - firefox
      - todoapp
    - "./error-shots:/usr/app/error-shots"
    - SELENIUM_ENV=selenium
    - TEST_ENV=todoapp

With this I was able to execute those tests using docker-compose without worrying about networking stuff: docker-compose run tests npm test

Of course, even with this simple application I’ve wasted some time to get the basics working and for this, I’ve configured a local instance of selenium:

npm install --save-dev wdio-selenium-standalone-service
./node_modules/.bin/selenium-standalone install
./node_modules/.bin/selenium-standalone start

Next I was ready to run wdio repl:

./node_modules/.bin/wdio repl chrome

With this debugging was much easier and a bit less frustrating ;)

My examples are hosted on GitHub and because of this I’ve decided to implement this solution in travis-ci (I am running this on gitlab-ci in a very similar way):

language: node_js
  - "8"

sudo: required


  - docker

  - sudo apt-get -qq update
  - sudo apt-get install -qy build-essential curl
  - docker build -t todoapp app/
  - docker run -td --rm -p --name selenium selenium/hub:${SELENIUM_VERSION}
  - docker run -td --rm -p --name todoapp todoapp
  - docker run -td --rm -e HUB_HOST=selenium -e HUB_PORT=4444 --name chrome --link selenium --link todoapp selenium/node-chrome:${SELENIUM_VERSION}
  - docker run -td --rm -e HUB_HOST=selenium -e HUB_PORT=4444 --name firefox --link selenium --link todoapp selenium/node-firefox:${SELENIUM_VERSION}

  - npm test

Be aware that for purposes of this demo I did some things that I personally consider bad practices. First of all, I’ve put node_modules in git to make todoapp working. Another bad practice was significantly increased test timeout (up to 30s) to avoid cleaning up after tests I just do browser.reload() which recreates user profile (about 10 seconds of overhead on each test).

With this I’m ready to write more e2e tests and get even more frustrated while doing so :) My initial experiences were pretty painful but I believe that right amount of critical e2e tests will help us to deliver better quality and allow deploy each commit on production with confidence.

15 Feb 2018 #docker #node #howto