PragPub 2011-04: Issue #22 by The Pragmatic Bookshelf

Author:The Pragmatic Bookshelf
Language: eng
Format: epub, mobi
Tags: PragPub—Monthly Magazine
Publisher: The Pragmatic Bookshelf, LLC
Published: 2011-04-01T04:00:00+00:00

digitalWrite(ledPins[mood], LOW);

mood = newMood;

digitalWrite(ledPins[mood], HIGH);

}

With this code loaded on the device, try rerunning your tests. You’ll need to set the MOOD_HAT environment variable to your Lilypad’s serial port, which might be COM3 on Windows or /dev/tty-usbserial-... on a Mac:

$ export MOOD_HAT=/dev/tty-usbserial-...

$ jruby -S cucumber features

Now, bask in the green glow of a stream of passing tests on your monitor.

Wrapping Up

What is it that we’ve done here? Well, I wrote this test suite for fun, just to see what kind of hoops one would have to go through to test an embedded device from Ruby. So, mission accomplished.

But despite my best intentions to keep this test suite purely theoretical, it ended up having practical value. Before all the LEDs were wired up, I wrote a temporary user interface that made just one LED brighter or dimmer to indicate the mood. Later, I could freely change the user interface and retest the underlying logic.

The tests were also a good place to explore different edge cases for the interface. For example: should the moods wrap around at the extremes, so that furious is one step happier than ecstatic? Definitely not, and this became clear as the different examples took shape.

Finally, there’s the more obvious benefit of using Cucumber to drive the design: the project now has a basic smoke test that can quickly be run against the firmware. As you write your own variant Mood Hat that’s way better than mine, you’ll be able to refactor fearlessly. When you do, please drop by the PragPub forums and show us what you’ve built.

The source code for this project is available here. You can see a video of the tests in action here. Happy hacking!

Special thanks to Maik Schmidt for reviewing this article.

By day, Ian Dees slings code, tests, and puns at a Portland-area test equipment manufacturer. By night, he dons a cape and keeps watch as Sidekick Man, protecting the city from closet monsters. Ian is the author of Scripted GUI Testing With Ruby and co-author of the upcoming Using JRuby.

Send the author your feedback or discuss the article in the magazine forum.

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