If you want to test the game before grabbing a copy, you’ll have a good chance.
You might remember the Global Testfire event for Splatoon 2 that offered the first chance to test the game before it was released. With Arms expected on June 16th Nintendo decided to prepare a similar event.
As you see in the title, it is adequately titled Global Testpunch. Once again the test will be available only in several time blocks, first of which will take place between May 26th and May 28th, with the second set planned between June 2nd and June 4th.
There are no exact dates shared at this moment, but you should visit arms.nintendo.com to get specific time slots for your region.