Gelael had his first experience of Formula One machinery driving the Toro Rosso STR12 at the in-season test after the 2017 Bahrain Grand Prix, completing 78 laps. He continued to drive for Toro Rosso in a testing capacity throughout the season, including tests at the Hungaroring and Yas Marina Circuit as well as Friday practice appearances in Singapore, Malaysia, the United States and Mexico. He continued his association with Toro Rosso during the season, appearing at testing days in Spain, Hungary and Abu Dhabi, and at the Friday practice session of the . In 2019, Gelael again took part in the post-season tyre test for Toro Rosso in Abu Dhabi.