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?
Update:
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".