Let’s change the word “test” to validation. 
Your signature is being recalculated after every activity or lack thereof (decay); no testing required.
Take a look at XO, Activities, Table. Note the figures fluctuate daily with or without validation.
Take a look at XO, Planner, Weekly Stats. Note the weekly delta for TP, HIE, PP.
If you do nothing but endurance rides below TP there aren’t enough data points to fully extract a fitness signature based on the three variables – threshold power, high intensity energy, and peak power. But calculated changes occur, nonetheless.
So yes, traditional tests (RAMP, 20, 8x2, KM) are bye-bye.
Maximal efforts on occasion to validate your signature? Not so much. They are still required.
You can noodle along for up to 3 weeks before XATA will display a triangle (!) warning below your name on XO – “Hey, where’s some maximal efforts?” [My words, not XATA.]
Time to validate your signature with a BT effort. Search the workout library for “breakthrough” and you’ll find a variety. You can be said and done in as little as 10 minutes worth of max efforts during a 30 minute workout with 10 min warm-up and 5 min cooldown. Nothing like a RAMP test but you can do one if you really like them. 
There is one in the Coach folder based on +6% TP steps.
Let’s say your signature is dialed in (validated recently) and you will be riding an extended period without maximal efforts. Base phase for example. Change the decay method to No Decay and the calculations will be based solely upon training load. With an IR set to Moderate-2 you are increasing TL week by week, so TP will rise little by little over that period. However, how well you are responding to that TL isn’t fully known unless you validate your signature periodically. You may have improved your fitness levels beyond the calculated numbers.
Compare that to someone who is putting in base miles but also inserting a ZRL or a hard group ride with sprints on a bi-weekly basis. They may never need to validate their signature with a BT workout. For best results, they should leave decay set to optimal, so a bit of decay occurs between their opportunities to express their fitness. Their signature change graph will be more step-like.