I hope that by the end of this I will have found the right words to say and questions to ask to get the battery tested for warranty service. Then I can share them here so others can have an easier time.
I saw on another post that MrDRMorgan bought the service manual, maybe they can look and tell me what page the battery testing procedure is on? Then I'll just go tell the dealer "I want the test described on page xxx"
I also have access to a service manual through an online subscription with ALLDATAdiy.com. I've been looking through the many technical service bulletins tonight and wasn't finding anything precisely named that would lead me to complete testing procedures, but I decided to comb harder through all the bulletins and I think I might have something very close to what you were asking for.
Here is the technical service bulletin for the Spark EV's High Voltage Battery Exchange Process. https://imgur.com/a/bb0fbRg
There are 9 pages to review. Within it, instructions on information collection and diagnosis start after "Recommendation/Instructions" on page 2. Hopefully, you can study and use the specific language to your advantage.
As a bonus, I just found a non-service manual archive for technical service bulletins, It's quite amazing how complete it is. Better than what comes with AlldataDIY's service manual and it's free to boot. Definitely adding this one to my arsenal.
Here is that bulletin I patched together earlier, except superseded to the most recent 2018 version. Looks clearer with better formatting and some added info. https://www.tsbsearch.com/Chevrolet/PIP5112R
Another, Warranty Administration – High Voltage Battery Exchange Process and Transaction Submission Information https://www.tsbsearch.com/Chevrolet/18-NA-180
Here's another bulletin where they share information on retrofitting 2014 vehicles with 2016 battery packs, perhaps for when they run out of A123 systems' LIFEPO4 packs? https://www.tsbsearch.com/Chevrolet/17-NA-003
Here is another technical service bulletin I came across regarding warranty administration in customer reimbursement. Maybe you can get reimbursed? https://www.tsbsearch.com/Chevrolet/11-00-89-004B
definitions for field action are here Field Action means any recall, removal, correction, or withdrawal, with respect to any Product.
And another one regarding dealer reimbursement procedures for advisor "empowerment tools". The framing is a little disturbing "...with enhanced empowerment tools, to drive more customers into GM dealerships...
If you want to search for other bulletins just filter by your make and model, and either filter for some keyword in the title or the TSB number.