TouK Hackathon – March 2019

Hackathons are prone to fail. It’s because we have very little time to create something useful, actually working and making a wow!-effect.

So this time we wanted to run “THE HACKATHON”, a well-prepared event with a very high success rate. We called it “Ship IT!” to ensure that we will focus on delivering a working product, not only on having fun while making it. We formed an organising team responsible for internal communication, collecting the needs, removing obstacles and buying some snacks and pizza for the event itself.

We thought that if we want to succeed, we’ll have to prepare well. So each team gathered before the event and talked about their plans, the technologies they intend to use and what hardware they need to order. The organizers met with all teams, exchanged details and gave some good advice.

And finally, the day has come! Seven teams started the two-day hacking session at 9AM, continued until 5PM, and showed the demos of all seven projects after 4.30PM on the second day. We gathered 25 participants total.

Here is a quick presentation of the projects we delivered.

Lidar/ROS.org based robot

robot image We always wanted to build a fully autonomous vehicle to transport sandwiches and monitor the Wi-Fi quality over the whole office space. The first step we took was creating a remote controlled platform with Lidar, which allowed to build the office map and made a foundation for future experiments. We reached this goal with ROS.org and mapped a few corridors and rooms in our office at the end of the hackathon. Now we’re almost ready to conquer Mars :D

Quak Liero-like Game

quak team Quak is a PvP platform game inspired by Liero or Soldat. We used a mix of Kotlin, libGDX and box2d (physics) to build a good-looking 2D game in less than 2 days. Destructible level as a mesh of boxes are generated from provided png layers. Additionally, we implemented some extras to diversify the player experience, such as multiple weapons, double jump, blood effects and explosions.

Quiz Game

quiz game DuckQuiz is a game we wanted to use at public event, e.g. conferences. It’s a little bit similar to the legendary Flappy Bird. Your goal is to make the title hero – a duck – go as far as possible! Correct answers give the duck a bump, so the more questions you answer correctly, the further the duck will go. Be careful, though! Three wrong answers will make a brick fall on the duck’s head! To spice things up a little, we decided to introduce a score threshold, which – once achieved – guaranteed a prize. Plus, of course, if you beat the highest score, you will make history as the reigning champion Duck Flyer. The quiz application is written in Kotlin for Android. We used RxJava and Retrofit for communication with the server. For the back-end side, we chose SpringBoot along with Kotlin. There is also a web-based “Hall of Fame” panel and a simple CMS which allows the management of the quiz questions, written in ReactJS.

Own Card Authorization system

demo4 We’re waiting for our private brand new vending machine which we’re going to use for distribution of snacks in Touk. We’ve noticed that we can communicate with it using MDB protocol. We’d like to authenticate in the machine with RFID cards which are commonly used in TouK to open doors. As a first step, we wanted to create authorization system based on RFID cards, but with additional PIN verification part added. Our system should be integrated with internal LDAP. We’ve separated our project into 4 modules: backend (spring boot), web frontend (scalajs-react), mobile app (android) and hardware device (arduino yun). Backend part connects all modules and allows matching RFID cards UID with LDAP logins. Web frontend is designed for users to set and manage their PINs. The mobile app at the moment is dedicated for our administrator to make pairing existing cards with LDAP logins easier. Finally, hardware device was created to read data from card, get PIN from user and check if PIN is correct (via backend). In the next step, we’d like to integrate our system with mentioned vending machine and make payments using it. There is also a plan to enhance mobile app and use it as mobile payment terminal and integrate web UI with Touk SelfCare system.

Notification lights

lights hackers Three suites (3 lights in red, yellow and blue) controlled by Raspberry Pi Zero W communicating with the managing service via MQTT protocol. The service handles messages from Rocket’s (our chat) outgoing web hooks and notifications from GitLab (e.g. opened merge requests).

Team gathering app (e.g. for football matches)

Team gathering app We regularly play football and volleyball after work, but we sometimes struggle with completing the teams. So far, we used a sign-up system based on Confluence pages, which is not mobile-friendly. We also wanted to allow registration for “reserve” players from outside the company. That’s why we built a simple mobile app with a sign-up form, game history and basic player ranking. The app was built with Dart using the Flutter framework and Firebase for storage and authorization.

Internal time reporting API

hr This HR project’s goal was to integrate and simplify the way we log time in our company. We’ve achieved that with a Google Calendar-like GUI and multiple microservices written in TypeScript, Python, Java and Scala!

The Grand Finale

demo1 At the end of “Ship IT!”, the teams had demonstrated the effects of their work. They shared some successes and other stories :) about the used software and hardware and the lessons learned during those two intensive days. The audience were amused when the robot started to explore the room. The Quak team had a bloody battle in their game. The lights were blinking when one of the team members wrote “kanapki” on our internal TouK chat.

demo2 demo3 demo5 demo6

It was very impressive that each team managed to deliver a viable result and show their projects in action. We can’t wait to run the next edition of The TouK Hackahton and hope there will be even more participants and surprising ideas to see.

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How to use mocks in controller tests

Even since I started to write tests for my Grails application I couldn't find many articles on using mocks. Everyone is talking about tests and TDD but if you search for it there isn't many articles.

Today I want to share with you a test with mocks for a simple and complete scenario. I have a simple application that can fetch Twitter tweets and present it to user. I use REST service and I use GET to fetch tweets by id like this: http://api.twitter.com/1/statuses/show/236024636775735296.json. You can copy and paste it into your browser to see a result.

My application uses Grails 2.1 with spock-0.6 for tests. I have TwitterReaderService that fetches tweets by id, then I parse a response into my Tweet class.


class TwitterReaderService {
Tweet readTweet(String id) throws TwitterError {
try {
String jsonBody = callTwitter(id)
Tweet parsedTweet = parseBody(jsonBody)
return parsedTweet
} catch (Throwable t) {
throw new TwitterError(t)
}
}

private String callTwitter(String id) {
// TODO: implementation
}

private Tweet parseBody(String jsonBody) {
// TODO: implementation
}
}

class Tweet {
String id
String userId
String username
String text
Date createdAt
}

class TwitterError extends RuntimeException {}

TwitterController plays main part here. Users call show action along with id of a tweet. This action is my subject under test. I've implemented some basic functionality. It's easier to focus on it while writing tests.


class TwitterController {
def twitterReaderService

def index() {
}

def show() {
Tweet tweet = twitterReaderService.readTweet(params.id)
if (tweet == null) {
flash.message = 'Tweet not found'
redirect(action: 'index')
return
}

[tweet: tweet]
}
}

Let's start writing a test from scratch. Most important thing here is that I use mock for my TwitterReaderService. I do not construct new TwitterReaderService(), because in this test I test only TwitterController. I am not interested in injected service. I know how this service is supposed to work and I am not interested in internals. So before every test I inject a twitterReaderServiceMock into controller:


import grails.test.mixin.TestFor
import spock.lang.Specification

@TestFor(TwitterController)
class TwitterControllerSpec extends Specification {
TwitterReaderService twitterReaderServiceMock = Mock(TwitterReaderService)

def setup() {
controller.twitterReaderService = twitterReaderServiceMock
}
}

Now it's time to think what scenarios I need to test. This line from TwitterReaderService is the most important:


Tweet readTweet(String id) throws TwitterError

You must think of this method like a black box right now. You know nothing of internals from controller's point of view. You're only interested what can be returned for you:

  • a TwitterError can be thrown
  • null can be returned
  • Tweet instance can be returned

This list is your test blueprint. Now answer a simple question for each element: "What do I want my controller to do in this situation?" and you have plan test:

  • show action should redirect to index if TwitterError is thrown and inform about error
  • show action should redirect to index and inform if tweet is not found
  • show action should show found tweet

That was easy and straightforward! And now is the best part: we use twitterReaderServiceMock to mock each of these three scenarios!

In Spock there is a good documentation about interaction with mocks. You declare what methods are called, how many times, what parameters are given and what should be returned. Remember a black box? Mock is your black box with detailed instruction, e.g.: I expect you that if receive exactly one call to readTweet with parameter '1' then you should throw me a TwitterError. Rephrase this sentence out loud and look at this:


1 * twitterReaderServiceMock.readTweet('1') >> { throw new TwitterError() }

This is a valid interaction definition on mock! It's that easy! Here is a complete test that fails for now:


import grails.test.mixin.TestFor
import spock.lang.Specification

@TestFor(TwitterController)
class TwitterControllerSpec extends Specification {
TwitterReaderService twitterReaderServiceMock = Mock(TwitterReaderService)

def setup() {
controller.twitterReaderService = twitterReaderServiceMock
}

def "show should redirect to index if TwitterError is thrown"() {
given:
controller.params.id = '1'
when:
controller.show()
then:
1 * twitterReaderServiceMock.readTweet('1') >> { throw new TwitterError() }
0 * _._
flash.message == 'There was an error on fetching your tweet'
response.redirectUrl == '/twitter/index'
}
}

| Failure: show should redirect to index if TwitterError is thrown(pl.refaktor.twitter.TwitterControllerSpec)
| pl.refaktor.twitter.TwitterError
at pl.refaktor.twitter.TwitterControllerSpec.show should redirect to index if TwitterError is thrown_closure1(TwitterControllerSpec.groovy:29)

You may notice 0 * _._ notation. It says: I don't want any other mocks or any other methods called. Fail this test if something is called! It's a good practice to ensure that there are no more interactions than you want.

Ok, now I need to implement controller logic to handle TwitterError.


class TwitterController {

def twitterReaderService

def index() {
}

def show() {
Tweet tweet

try {
tweet = twitterReaderService.readTweet(params.id)
} catch (TwitterError e) {
log.error(e)
flash.message = 'There was an error on fetching your tweet'
redirect(action: 'index')
return
}

[tweet: tweet]
}
}

My tests passes! We have two scenarios left. Rule stays the same: TwitterReaderService returns something and we test against it. So this line is the heart of each test, change only returned values after >>:


1 * twitterReaderServiceMock.readTweet('1') >> { throw new TwitterError() }

Here is a complete test for three scenarios and controller that passes it.


import grails.test.mixin.TestFor
import spock.lang.Specification

@TestFor(TwitterController)
class TwitterControllerSpec extends Specification {

TwitterReaderService twitterReaderServiceMock = Mock(TwitterReaderService)

def setup() {
controller.twitterReaderService = twitterReaderServiceMock
}

def "show should redirect to index if TwitterError is thrown"() {
given:
controller.params.id = '1'
when:
controller.show()
then:
1 * twitterReaderServiceMock.readTweet('1') >> { throw new TwitterError() }
0 * _._
flash.message == 'There was an error on fetching your tweet'
response.redirectUrl == '/twitter/index'
}

def "show should inform about not found tweet"() {
given:
controller.params.id = '1'
when:
controller.show()
then:
1 * twitterReaderServiceMock.readTweet('1') >> null
0 * _._
flash.message == 'Tweet not found'
response.redirectUrl == '/twitter/index'
}


def "show should show found tweet"() {
given:
controller.params.id = '1'
when:
controller.show()
then:
1 * twitterReaderServiceMock.readTweet('1') >> new Tweet()
0 * _._
flash.message == null
response.status == 200
}
}

class TwitterController {

def twitterReaderService

def index() {
}

def show() {
Tweet tweet

try {
tweet = twitterReaderService.readTweet(params.id)
} catch (TwitterError e) {
log.error(e)
flash.message = 'There was an error on fetching your tweet'
redirect(action: 'index')
return
}

if (tweet == null) {
flash.message = 'Tweet not found'
redirect(action: 'index')
return
}

[tweet: tweet]
}
}

The most important thing here is that we've tested controller-service interaction without logic implementation in service! That's why mock technique is so useful. It decouples your dependencies and let you focus on exactly one subject under test. Happy testing!