I am not sure what a VMA test is but many all out or pacing test are best done in slope mode. I prefer ramp tests but there advantages and disadvantages to different tests.
I believe he’s asking about a VO2 Max test. Vitesse Maximale Aérobie (Aerobic Maximum Speed), which is a physiological measure used in endurance sports like running and cycling. It refers to the minimum speed at which your body reaches its maximum oxygen consumption (VO₂ max)