Agile Software Development Saves Lives!

Agile Software Development Saves LivesAhem. Actually that’s a bit of an exaggeration. I have to be honest with you. Agile software development probably doesn’t really save lives. There, you heard it from me first. I just felt like being melodramatic…

Someone once joked with me that “agile is great, but you wouldn’t use it
on an air traffic control system!”

Actually, I would.

In fact, I wouldn’t dare use anything else.

But agile is just a concept – a set of values and principles. What specific agile practices would be most appropriate in a life or death situation like this?

Those who read my blog will know I’m a big fan of Scrum. I have used Scrum on its own, without any other agile practices, and with a great deal of success. I would probably still use Scrum as the management approach to an air traffic control system, but I certainly wouldn’t use it on its own.

For a project like this, where quality is absolutely critical and lives depend on it, I would put a strong emphasis on XP (Extreme Programming).

Personally I would describe Scrum as an agile management method, whereas XP is more about agile engineering and XP has some important practices to assure quality.

One is Pair Programming. If we’re going to write code that people’s lives depend on, there’s no way I would want a single line of code written by any one person. I would want every line scrutinised, every assumption challenged, and every line sanity-checked with a second pair of eyes. With Pair Programming, this level of continuous peer review obviously comes as standard.

Another QA aspect of XP is automated unit testing and Test Driven Development (TDD). On a project like this, I would want 100% test coverage. I would want to know that every scenario had repeatable tests, so we could be completely sure that nothing ever regressed after passing the initial tests without us knowing about it. Anything less would simply be inadequate.

There are many specific practices in Scrum and XP that would help to mitigate risk and assure quality on a project as critical as an air traffic control system. But these two practices in particular – Pair Programming and Test Driven Development – if followed religiously, I am sure would deliver higher quality code than any other approach to development and testing.

In commercial situations, this level of rigour isn’t always appropriate or affordable. But when quality is paramount, these engineering practices make complete sense. For an air traffic control system, the overhead of doing them 100% of the time is completely justified by the lives they could save.

In a situation like this, I wouldn’t have it any other way.


Photo by Akinori YAMADA

4 Responses to “Agile Software Development Saves Lives!”

  1. wic says:

    I agree, but just wanted to point out that XP does in fact contain pretty much everything when it comes to planning, stories, retrospective etc. XP is more than just a handful of programming practices.

    I tend to be skeptical about teams who "only" uses Scrum. Things usually starts of well but after a while they amass lots of technical dept because scrum does not bother with the engineering practices. This is a problem with Scrum imo.

  2. Pawel Brodzinski says:

    Would you write unit tests for setters and getters in interfaces too? Otherwise you wouldn't have 100% coverage anyway.

    I'm just being curious. I actually don't believe much in value of having 100% code coverage. What works better for me is having developers who consciously decide whether to write a test or not and if their decision is positive what king of tests these should be.

    Key value of unit tests is brought by testing marginal conditions and standard 2+2 test covers the code exactly the same as several tests checking specific cases.

    This is by the way the reason why I don't expect to see 100% coverage.

  3. Stephen says:

    The whole premise of the title statement (or rather from its opposite) is misleading, and, IMO, stems from the general misconception about agility.

    The issue with developing mission/life-critical systems is not about agility but about quality. You correctly identify XP as possessing some practices that help ensure quality. The benefit of Scrum would be that flaws in critical components would (ideally) become manifest early, contributing to guiding the development process.

    Unfortunately, quality is something that is as easily overlooked in so-called agile projects as in more traditionally-modelled counterparts.

  4. MyOpenDraft says:

    Nice post ;) we should consider different factor when adopting agile in enterprise, i think the most effective way is to evaluating different agile practices and applying hybrid model in your organization.

    You should do what you need and ignore other practices if you think it's not effective for your situation.

    Just learn from mistake and apply process improvement technique.

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