For cycling we use a whole range of systems depending very much on what you want to achieve, what your experience is, what equipment you have.
However we work on heart rate and power. Most people have a heart rate monitor. Now you can buy chest straps that work with your smart phone.
We Test using power and heart rate. To achieve this we test people using either Garmin Vectors or a Computrainer or there own turbo. My belief is that the tests need to be repeatable, otherwise there is no point doing them, you want to know if you are improving or not. It is a measure of both you and me.
The old adage of ‘ride your bike, ride your bike, ride your bike’ works, but only if you have a lot of time to ride your bike. When time starved or weather inhibited there are more effective ways to improve than going for a ‘pootle.’
However we have to accept that we are not all going to be Olympic Champions