What is involved with individual user-testing?

You individually test every minor detail and aspect of your game, keeping a
running list of your individual observations and noting things you would like to
change.

You ship your game out to several hundred users and ask them to fill out a
reflection survey and send it back to you after they test your game.
You observe a user playing your game or prototype by them recording
themselves while playing remotely or, more ideally, you observe a user playing
your game in person.

You choose five professional gaming individuals to test your game and create a
reflective report regarding what they liked and didn't like.