That is the best way to go, no need to re-test to get some supposed “accurate/exact” FTP number. You’ll know soon enough if workout are too easy/hard based on the IF, the workout description/intentions and your RPE.
I had a similar “bad ramp test”, due to the fact that I was using PowerMatch for the first time and I may have reached the trainer’s power ceiling. So my poor test was because of equipment/software communication failure having trouble with my low cadence and high power at the end of the ramp test. See below…
I had my head down at the end of the ramp test and thought I was grinding out the last 1:30 of the test, only to stop and find out I was way under the target power. I was initially very upset and frustrated. But after I slept on it and then looked at my past weeks and months workouts, I realized that my fitness had been steadily increasing. I had increased the intensity in some workouts in the past weeks and felt strong in the final work week before my recovery week. Also, each of my previous FTP tests I had a 2% increase.
So instead of retesting or being frustrated by my “bad ramp test”, I simply raised my FTP by 2% and the first workout so far felt right. I will continue to evaluate this new FTP and determine if it feels appropriate per the IF and the workout description/intention. I’ve done enough TR workouts over the past 9 months that I know how certain zones should feel. It’s easy to get caught up in FTP tests and their accuracy etc., but once you start doing the workouts you should know soon enough if your FTP is correct or not. If its not you simply adjust accordingly.