Coding Horror

programming and human factors

The Ultimate Unit Test Failure

We programmers are obsessive by nature. But I often get frustrated with the depth of our obsession over things like code coverage. Unit testing and code coverage are good things. But perfectly executed code coverage doesn't mean users will use your program. Or that it's even worth using in the first place. When users can't figure out how to use your app, when users pass over your app in favor of something easier or simpler to use, that's the ultimate unit test failure. That's the problem you should be trying to solve.

I want to run up to my fellow programmers and physically shake them: think bigger!

A perfect example of thinking bigger is Alan Cooper's Interaction 08 keynote, An Insurgency of Quality.

Alan Cooper's Insurgency Talk video

There's a transcript of his keynote available, or you can view a video of his keynote video with the slides in place.

Alan is a well known interaction designer , and the author of several classic books in the field, such as About Face, and a few others that are on my recommended reading list. In the Q&A after the talk, he had this to say:

"We are not very important because we don't cut code." (A boo and hiss from the audience.) In the world of high-technology, if you cut code, you control things. It's the power to destroy the spice, it's the power to control the spice. It's not a fine kind of control: it's bruce-force kind of things. [Interaction designers are] largely marginalized. We're constantly asking for permission from the folks who shouldn't be in a position to grant permission. We should be working with business folks and marshalling the technology to meet the solutions to business problems.

But when it comes time to marshal the solution to the problems, we find ourselves slamming into this kind of Stay-Puft Marshmallow Man of software development.

Stay-Puft marshmallow man, from Ghostbusters

We don't need to change interaction design; we need to re-orient organizations to build things right. When we come to programmers and say, "Look at the people I've talked to; look at the personas I've created" and present them with research, programmers understand that, and that's how we will influence.

It pains me to hear that Cooper considers most programmers twenty-story marshmallow barriers to good interaction design. Please don't be one of those programmers. Learn about the science of interaction design. Pick up a copy of Don't Make Me Think as an introduction if you haven't already. There's a reason this book is at the top of my recommended reading list. Keep your unit testing and code coverage in perspective -- the ultimate unit test is whether or not users want to use your application. All the other tests you write are totally irrelevant until you can get that one to pass.

Written by Jeff Atwood

Indoor enthusiast. Co-founder of Stack Overflow and Discourse. Disclaimer: I have no idea what I'm talking about. Find me here: