Kristel Kruustük: “You can never please everyone” 14.05.2019 Liisi Mölder, Birgit Püve Kristel Kruustük, 29, is the co-founder of Testlio, a startup that tests software. Nominated ‘Entrepreneur of the Year’ in 2017 in Estonia, she’s the youngest female millionaire in the country and a prominent figure in the European tech industry.