How do you test a motor in Betaflight?
The easiest way is to test your motors using the motor tab in Betaflight. Many other flight software offer similar “motor testing” feature including KISS, FlightOne, Cleanflight and Butterflight. This is also available in ESC configurator – BLHeliSuite too.
Why do quadcopter motors spin up by themselves with props off?
Hence change over time. What you’re seeing as the motors slowly spin-up is the buildup of that Ki value getting stronger and stronger as flight controller is trying harder and harder to execute a change that it can sense, but can’t impact. No props means no force to execute change, hence the windup.