"A first-come, first-serve basis".
Nintendo has announced it will perform a test called the 'Nintendo Switch Online: Playtest Program' which is related to a new feature for the online service available on the Switch.
It plans to recruit people to participate in this test from customers who already have an active NSO + Expansion Pack membership. If you are invited, you'll need to then download "exclusive software" to your Switch to participate.
Read the full article on nintendolife.com