The ARMS Global Testpunch kicks off next weekend which will allow Switch owners to try the game online for a few days on certain dates. In order to participate you will have to download the Testpunch demo which is available on the eShop. To make sure that we only get a taste of the action, we will only be a able to play standard online matches and not all the characters from the roster will be playable.
You will be able to choose between Spring Man, Ribbon Girl, Master Mummy, Ninjara, Mechanica, Min Min & Helix. The three new characters that were announced at the latest ARMS Direct; Kid Cobra, Byte & Barq, and Twintelle will not be included but at least we still have a varied roster of characters to chose from.
— ARMS（アームズ） (@ARMS_Cobutter) May 19, 2017
Source: ARMS Official Twitter Page