Tuesday, 14 January 2014

Functional Testing Starling Applications with Cucumber and Melomel Redux - Part 1


A few months ago we decided to embark on a cross platform application for our store staff, there were three criteria which the application must meet:

1. It must be fun.
2. It must be cross platform.
3. It must be fun.

After spending some time thinking about what we wanted to do we realised that we wanted the app to feel like a game. We then had the harsh realisation that this was not going to be easy to code, in fact after running up some rough estimates of effort we realised that it was also going to be expensive to build native.

We did some research and concluded that HTML5 would not give the performance we wanted from animation on mobile platforms and that we did not really want to use Unity.   Having read a lot about Starling and the amazing cross platform performance we decided we would give this a go and started to build our stack around the Starling framework.  Both Keith and I used to be Flash programmers back in the day when Flash was still owned by Macromedia and both of us have a warm place in our hearts for ActionScript so coding in Starling should not be too alien.  Zan an Android developer who we had just recruited stupidly expressed interest in the project and having no past experience in either ActionScript or Flash was thrown straight into the deep end.  Alex an epic JavaScript developer who saw trouble a mile away was press ganged onto the project and we had our merry band.

One of the things we have been concentrating on at Marks and Spencer has been solid engineering principles, we have spend a lot of time working on Agile practices, Continuous Integration, TDD and BDD using cucumber.  Personally I have bored myself silly telling the developers about the virtues of Test First Development, how important CI is, etc, etc.

When we were putting together our stack for the app we decided that we would use Starling but we would also implement the Pure MVC framework to give us clean separation and testability.  We would write everything full TDD and we would have full automated functional testing.

Tech spike time and it did not go well, due to inexperience we battled with flex unit so dropped it, we could not work out how to test the Pure MVC components in isolation so we didn't, we could not find a functional testing frame work so we decided that our poor automation tester Anu would manually test the app, she still hates us and I don't blame her.

So in effect we decided to do everything that modern development methodology tells you not to and funnily enough we ended up in exactly the same mess that conventional test driven development is intended to avoid.

Post delivery of the app which was not a great success due to a large number of defects, these were eventually fixed but we realised that we could not continue developing in this way and had to either:

1. Change core technology to something which we can write tests for.
2. Write some testing frameworks.

We chose 2, mainly because I like Starling, and secondly because I refuse to admit I was wrong about choosing it in the first place.

Now Paul who works for us used to work for the BBC building their iPlayer application in Flex, he suggested we look at a framework called Melomel written by Ben Johnson (https://github.com/benbjohnson/melomel).  I took a look and it is indeed a very impressive framework however incompatibility between flash.display.DisplayObject and  starling.display.DisplayObject meant we could not use it.

Unless we modified it.

So we did (https://github.com/DigitalInnovation/melomel).

Melomel had not been touched for a couple of years and needed a little love so we abstracted out DisplayObject and its descendants into a common interface, modified all the tests, wrote implementations for starling objects, wrote a whole heap more tests added touch and swipe functionality and ended up with a rather nice Cucumber framework that allows us to interrogate and interact with our Starling applications.

In part two I am going to show you how to build and launch your application using a Rake not an IDE and get your initial cucumber framework setup.


  1. Following these series of posts with great interest. Looking forward to part 3. Thanks for sharing your insights around functional testing, BDD to improve quality within starling /actionscript focussed applications (inc other refreshing work around crash reporting for Adobe AIR via RaygunAS)

    In short; 'good stuff guys!'