Webster's Revised Unabridged Dictionary · 1913

Testy

Testy , adjective

[Old French testu obstinate, headstrong, French têtu, from Old French teste the head, French tête. See Test a cupel.]

Fretful; peevish; petulant; easily irritated.
Must I observe you? must I stand and crouch Under your testy humor? — Shakespeare
I was displeased with myself; I was testy. — Latimer