Click everything. Type nonsense. Hand it to someone who was not in the room while you built it.
Walk the main path first: the one thing this exists to do. Then walk the awkward paths—empty states, wrong dates, missing photos.
Write down what confused you in the moment. Confusion fades fast and you will not remember it later.
A relative who has never seen the project is worth more than an hour of your own testing.
Practice
Test on a phone before you test on a laptop.
Try this
Ask someone to complete one task while you stay silent and watch.