[Update: The western network test will run from May 11-12 from 6:00 PM PT until 11:59 PM PT on PS4 and Xbox One. You can download the test client from today until May 8 at 11:59 PM PT.]
The Dark Souls Remastered network test that was teased during Nintendo's direct will soon be launching for PS4 and Xbox One. On May 11 and 12, you'll be able to experience the updated version of FromSoftware's classic title as well as check out how the multiplayer has been expanded beyond the original title. If you live in Japan, you can also pre-load the beta from your digital storefront of choice right now. The US version (if it is occurring on the same date) has not gone live yet.
I'm assuming the delay for Nintendo's console is why the Switch won't currently be hosting this test. Either way, the little I saw of it at PAX was reassuring, so I wouldn't have any fears that the Switch port will be great.