Took a first look at the Lightning Testing Service (LTS) that is in (open) pilot today:
In its present form it is an unmanaged package meaning you have components and static resources added to your org and so your version control system.
Will the delivery mechanism change for GA? (Wondering whether if I add the components etc now I will have unused debris left in the future.)
LTS has been an unproductive tool for us; our hope is that the LWC testing tools are much, much better.