Add automated UI testing

[marisademeglio]

As an electron project, the Pipeline UI could incorporate selenium for automated UI tests.

[marisademeglio]

I started working on this but ran into issues connecting Chromedriver to our electron UI. I think it has something to do with how we create the UI windows, because it works for a generic electron app.

I also had an idea and started experimenting with programmatically convert existing xprocspec tests to automated UI tests: a parser would fetch the xprocspec tests from the Pipeline repo and convert them into a series of jobs (what script, what inputs, and expected outputs) which then get executed in the UI itself. Then it would check and see if the correct output was generated.

I would like to pick back up with this at some point; having a good automated test suite will save us headaches in the future. For now I'm leaving this comment here for future reference. I will push my WIP branch at some point too.