Improve your Feedbackloop with Continuous Testing

Have you ever though about what the most valueable thing in software development was for you? And im not talking about things that value for you personally, but for the success of the development itself. Well i have thought about it, and for me it was Feedback - in any form. It is so important, because it enables steering. Development practices are made for the purpose of better feedback. TDD, Continuous Integration, Iterations, to name only a view. Many of the agile methods and XP are basically about better feedback.

It begins with customer interaction. I need as much feedback as possible, as frequent as possible. If i don't get feedback, i'm likely to get on the wrong track, resulting in a product that is not going to be used, because it's not what the customer needed. The more feedback i get, the better the outcome will be. If i get feedback rarely, i am unable to steer. I'm forced to make assumptions which are likely just obstacles. The quicker i get feedback, the faster i can deliver value to my customer. Feedback allows me to steer.

Feedback is as important for programming. I want it early and often. If i write hundreds of lines of code without running them, they will most likely result in a very long and painful debugging session, and a lot of changes. I don't want that, so i take baby steps. They make me go safer, faster and happier. There are two phases that define my programming feedback loop.

1. The phase where i write code. Lets call it alpha, like so 'α'.
2. The phase where i evaluate my code, and eventually fix errors. Lets call it beta, like so 'β'.

You could also see those phases as modes. It is important to understand here, that these phases have nothing todo with the alpha/beta definition of a software cycle. I just invented them to describe my programming feedbackloop.In the following graphics you'll notice that the lines get shorter and shorter by example which is intentional and should point out how i got faster using new strategies.

When i first started coding, i did not write any tests. I wrote lots of code before i tried it out manually. Obviously it didn't work when i first ran it. I ended up in rather long α-phases, where i just wrote code, and also long β-phases, where i evaluated (got my feedback), and fixed it. Like this:



I was very slow back then.

I soon started with an interpreted language, which was very cool because i could run the scripts immediately. No need to compile or anything. Just write and run. It shortened my feedback loop, and i became faster overall:



Sooner or later i eventually started tdd. And regardless of the language that i was using, interpreted or not, it again shortened my feedback loop and made me go faster. The loop was shortened to a single 'unit', which is obviously smaller than anything manually executable. It allowed me to evaluate small behaviours, long before the program was even runnable. It is important to understand, that the α-phase in the following graphic contains both writing tests and implementation. The β-phase is much shorter, since unittests run very fast.


I thought this was just great, and it could not get any better. Wrong i was!! Later, i tried something that made me go like this:



"What the ...?" You might ask. No, i did not break space-time. The thing i tried was Continuous Testing. Which basically means, that i do tdd, but i don't run my tests by pressing a button and then wait. I just have them run all the time in the background automatically... Everytime i change my code, my tests immediately run automatically, and show me "OK" or "NOT OK" on a small icon on my screen. Since the tests only take about a second to run, this feedback is instant. And since my IDE saves my files onchange automatically, i do not have to press ctrl+s or anything. I just code... and as i code my files get saved.... and as the files get saved my tests get run... fluently, immediately. This is HUGE. I am now progressing without disruption. I completely broke out of the phases, or if you want to call them 'modes'. I love it.

I have used infinitest for this. It is a Continuous Testing plugin for Intellij/Eclipse. If you are doing javascript, i can also recommend grunt for Continuous Testing.