The paper test: see what actually drops
Begin away from the water. Mount the feeder where it will sit, run it over a sheet of plain paper for several cycles, and compare each pile with a feed you would give by hand. Most feeders arrive set far too generously, and a drum that looks modest can drop three days of flake in one turn. Adjust the aperture or portion setting down until one cycle lands one honest feed, then run several more cycles to confirm the amount is consistent; a feeder that portions randomly has failed its first test and goes back in the box. Mark the correct setting with a pen line so a knock cannot silently change it.
Test with the trip's real food
Feeder behaviour is food behaviour. Flake absorbs moisture from the tank's surface, clumps, and can bridge over the outlet until nothing drops at all; small pellets flow freely until one lodges and jams the drum; granules sit somewhere between. Whichever food the trip will use is the food the test must use, loaded to the same level you will leave it. If your fish eat a mix, simplify the holiday menu to the single most reliable food rather than asking a rotating drum to handle variety. A week of boring, successful drops beats one exciting failure on day nine of your trip.
A week over the living tank
Paper proves portions; only the tank proves the system. Run the feeder as the tank's only food source for at least a week while you are home, watching the drop land in open water rather than on the lid, a plant or the filter outflow that whips it straight into the intake. Watch the fish feed from it, and watch the water: cloudiness or food settling uneaten means the portion is still too big however neat the paper piles looked. Check the drum each morning for the humidity crust that builds above warm water, because that crust is the jam forming in slow motion.
Power, position and the pre-trip reset
Treat batteries as a consumable, not a component: fit fresh ones the day before any trip even if the indicator claims plenty, and leave the spares beside the tank for a mid-trip sitter. Position the feeder firmly so a curious cat or a closing lid cannot shift it, with its outlet over the feeding area and clear of the light unit's heat. The day before departure, empty it, wipe the drum dry, refill with fresh food from a newly opened packet if the old supply has sat open for months, and run one witnessed cycle. That final watched drop is the feeder's signature on its own test certificate.
Writing down what tested-correct looks like
A tested feeder still needs its evidence where a checker can use it, because 'the feeder is on' means nothing to a sitter who has never seen it work. Your KinsLe Care Pass can carry the model, the marked portion setting, the food loaded and the drop time, so the person glancing in mid-trip compares the tank against the tested setup, and a drum found full on day ten reads instantly as a failure to report, not a mystery to solve.