Hey JB,
We recommend doing testing during your transition weeks and you can replace the tempo run with a full field test or do a modified field test. However you can do the talk test in replacement of a foundation Run on any week if you want to get your zone info sooner.
Check out this resource on testing options and if you scroll to the bottom you will find more details on our advice for keeping your zones current.
Intensity Guidelines for 80/20 Running
Leyla