I had two main questions going into the user testing: could a user discover all the functionality of Pelagios, and could they make sense of what they were shown? In short, the answer to the first question is 'no', and the answer to the second is 'yes'.
I'm a big fan of testing the usability of a site with real users. Test participants not only give you incredibly useful insights into your site or application, but they help you clarify your own thoughts about the design. It was exciting to see test participants realise the potential of the site - particularly the map and data views, which is a cue to make them more prominent when the site first loads - but it was clear that the graph interface needs improvements to make the full range of actions available for selecting, linking and exploring datasets more visible to the user. The test participants also used search heavily when looking for particular resources, so this would be a key area for future work.
If you've been working on a project, user testing is wonderful and painful in equal measures. It's definitely easier to test someone else's project, not least because it's easier to prioritise tasks from the users' point of view when you don't have to deal with the details of implementing the changes.
The overall goal of the usability testing was to produce a prioritised list of design and development tasks to improve the usability of the Pelagios visualisation for a defined target audience (non/semi-specialist adults with an interest in the ancient world), and this user testing was really successful in giving the team a clear list of future tasks.