April 12 is the 60th anniversary of the first human spaceflight, Vostok 1. As no human had previously been to space, it was also a test of the SK-1 spacesuit that cosmonaut Yuri Gagarin wore.
This question asks about how early spacesuits were tested; the answer explains that they were laboratory tested in a vacuum chamber. Was the SK-1 actually tested in an aircraft or spacecraft prior to Gagarin's flight?
This is the first of 6 questions honoring the 60th anniversary of Vostok 1, the first human spaceflight.