Yes! In fact I started working on this yesterday. Hopefully I can get this finished up next week, and will be adding it to this sample:
...so keep an eye on that repo.
I added some UWP, iOS and Android unit tests to the Office Locator Sample here:
It's not anywhere near 100% code coverage, but just to serve as an example, and just chooses one of many test frameworks out there (I just happen to know MSTest and MSTestX the best).
However to be clear: There really isn't anything special about unit testing ArcGIS Runtime Apps. If you want to learn more about how to unit test your apps and libraries, I'd really recommend almost any unit test and/or UI Test tutorial for the platform that you're writing for, and choose the framework that best suit your need. We're really great at writing GIS related libraries, but we leave some of the more generic developer topics to the people who specialize in those things.
I'm curious if you were looking for any GIS specific testing, that isn't already covered by "normal" unit testing?