Jaminb unless you were already in pretty decent condition before starting if you’ve done six weeks of 3/4 structured sessions I’d be surprised if you haven’t seen a decent jump.
The question is how’d you wanna test it?
Did you do a test at the start, the fairest way is to test in the same way.
If you didn’t do a test at the start you’ve got a few different options.
Ramp Test – this is quick if a little brutal, if you’ve not done one before you’ll prob underperform as there’s def a knack to them.
There’s the long test, I wouldn’t bother as a you can do the same in a group ride or race.
I’d go for a race, enter in Cat D try as hard as you can for twenty minutes and then see if you’ve got anything left after that. A bunch of different routes to choose but I’d just chose the event with the biggest number of entrants so there’s plenty of wheels to chase to keep the motivation up