If you signed up for the Android only Mario Kart Tour beta test you may have this email waiting for you.
It appears that the beta test is going to run from May 22nd through June 4th. Afterwards players will receive a survey asking them about various different elements of the game to address any issues. It is unknown why this is an Android only beta and nothing regarding an iOS beta was announced. Sadly, this test is under a strict NDA and we shouldn’t expect to see many, if any, screenshots or videos unless purposely posted by Nintendo.
Mario Kart Tour was originally supposed to come out by the end of March 2019 but was then delayed till Summer 2019. Judging by the beta announcement, the summer timetable seems right unless something terrible is uncovered in beta. For more information regarding Mario Kart Tour head on over to the official site.