[1] Louis' younger brother was the painter Henri Testelin, secretary to the Académie royale de peinture.
[1] His family was Protestant and Louis remained so until the end of his life, though this did not impede his career - he painted for Anne of Austria and accepted commissions from several monasteries in Paris.
He studied under Simon Vouet and became a friend of Charles Le Brun, who was working in the same studio.
According to a biography edited by Georges Guillet de Saint-George, Testelin and Le Brun collaborated "on some paintings and decorative schemes" for the former church of Val-de-Grâce.
He also painted the Mays for 1652 (Saint Peter Reviving the Widow Tabitha, now in the Musée des beaux-arts d'Arras) and 1655 (The Whipping of Saints Paul and Silas).