I am the same, I train at approx 0530 in the morning, I do not eat before hand, I sometimes have an espresso if it looks like a hard one. I’m good for all workouts up to 90 mins (have never done a longer one) I’m on LV plans. Why would you test strong if you’re going to train at maybe a slightly less optimum time? I do not see the logic behind this idea.
Sure, if you’re racing by power numbers then you’ll need to know your stronger FTP in order to produce the best race but if you’re calculating FTP for training then do it when you’re aiming to train.