Karstenl - that did it. I was having a hard time translating IOS to Meraki-speak, so to speak, and didn't understand how to assign an individual SVI IP to the test switch so that the stack and the test switch were in the same VLAN. I initially created the SVI on the test switch, but did not have the corresponding interface configured on the stack.
I deleted the SVI from the test switch and created it on the stack, then figured-out how to add an SVI with a unique IP in the same VLAN on the test switch, and now the two are neighbors and routes have been exchanged.
Thanks for your help. I learned something today.
Twitch