Testut entered 2 Formula One World Championship Grands Prix, both in Monaco, in 1958 and 1959. On both occasions he drove his Maserati 250F and both times he failed to qualify. In 1958 he also entered a car for Chiron. For both drivers it would be their last attempt to race in Monaco. Tesnut performed better at the 1958 Syracuse Grand Prix when he retired with engine failure when he was running seventh with ten laps to go.