On rollers, this is suboptimal. 
Be great if the ramp test would auto-end when it detects much lower wattage for a period of time (e.g., 50% lower than the current step for >10s). That way I wouldn’t have to fumble for my phone to stop the test and can just keep pedaling easily to spin out the legs.
At the very least, the ramp test screen should have a persistent End Test button to make it easy to stop with one tap (which I’ve requested before).