Took a first look at the Lightning Testing Service (LTS) that is in (open) pilot today:
The Lightning Testing Service, or LTS, is a set of tools and services that let you create test suites for your Lightning components using standard JavaScript test frameworks, such as Jasmine.
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.)
See What to Javascript-test in Lightning components and what not for some other discussion on LTS.
PS
LTS has been an unproductive tool for us; our hope is that the LWC testing tools are much, much better.