UI testing

[NickHu]

The architecture of the program is well-suited for unit testing (every UI state can be reached by an appropriate sequence of Actions, which is extremely easy to encode versus something like "click on this part, wait for it to load, activate this button"). In principle, it should be easy to write unit tests to ensure that it behaves nicely using this approach, and we should, but it's not something that we do currently.

[NickHu]

@zrho knows more about this, anything to add?