I use a KK dumb trainer right now also, and for sure I also have to plan ahead with gearing. Usually what I do is plan a few steps ahead and sometimes start at the low end of my comfortable cadence range but then work my way into a better cadence for those final steps where it really matters.
Regarding the original question, ramp test all the way! I’ve found the results of the ramp test to be consistent with 8-min test (I rarely have done the 20-min test). If you start out the workouts and they are exceptionally hard that you fail, or very easy… then you might adjust like those in the posts mentioned above.