Observing representative users carry out representative tasks using a system (for example, your data visualisation tool), and recording any issues that come up!
Ideally, there’s a participant (a user to test your system), facilitator (that might be you), and observer (let them take notes).
A quick overview
A critical part of evaluating something that you’re designing and developing is to observe real users using it.
It isn’t about getting the test participants to design it for you. It also isn’t about finding out whether something is a good idea (i.e. whether or not you should put development effort into some feature). That is another thing altogether, and really part of an earlier phase of exploration and learning in the design process.
In essence, usability testing is pretty simple – find things that trip people up in the interaction design of your product, and then fix them. The key principles to remember are that you should test whatever you’re working on as early as you can, commit to fixing usability issues that come up (especially big things!), and then test again. This iterative process allows you to hone your product as you develop it. It’s not about ticking the “usability testing” box on your checklist!
Committing time to prioritising and fixing problems that come up is very important, otherwise they aren’t going to just go away! As a great example of acting on usability test findings, my colleague, Sangya Pundir, UX analyst for UniProt, works with developers to prioritise usability issues in terms of frequency and severity, and then adds these as “bugs” in a Jira bug-tracking system. The developers work directly from this, and it’s a great way to make sure that fixing these issues is part of (rather than as well as) a developer’s normal workflow.
I mention there that you should get hold of a copy of Steve Krug’s book “Rocket Surgery Made Easy“. See also “The Handbook of Usability Testing” by Jeffrey Rubin and Dana Chisnell. For a deeper look at usability testing and evaluation in general, I’d also recommend “User Interface Design and Evaluation” (Stone, Jarrett, Woodroffe, Minocha).
You can download a copy of the handy Top Three Usability Issues sheet, too.