I am about to upgrade from Android K to Android L. Right after, I will upgrade from Android L to Android M.
In a previous empirical experiment, with a now-demised device, I noticed (or seem to have noticed) that the battery life seriously degraded after upgrading Android.
Even after a good month of daily charging and discharging (from 0% to 100% and back), in the vain hope of properly recalibrating the battery, the lifetime was still down to about 8-10 hours from about 14-16 hours.
This time I would like to be able to prove it.
What is a canonical battery test that I can run (now and after upgrading) to determine whether upgrading deteriorated the battery life? I imagine that viewing a 6-hour YouTube video and noticing how far it goes would do the trick, but it's also very skewed to a single task. Is there an alternative that better represents the daily activities with an Android phone?
In addition to beeshyams's answer I'd like to point to Firelord's suggestion to use GSam, which does provide an ongoing "Averages Per Complete Charge".