Source : Webster's Revised Unabridged Dictionary (1913)

Testy \Tes"ty\, a. [Compar. {Testier}; superl. {Testiest}.] [OF.
   testu obstinate, headstrong, F. t[^e]tu, fr. OF. teste the
   head, F. t[^e]te. See {Test} a cupel.]
   Fretful; peevish; petulant; easily irritated.

         Must I observe you? must I stand and crouch Under your
         testy humor?                             --Shak.

         I was displeased with myself; I was testy. --Latimer.

Source : WordNet®

testy
     adj : easily irritated or annoyed; "an incorrigibly fractious
           young man"; "not the least nettlesome of his
           countrymen" [syn: {cranky}, {fractious}, {irritable}, {nettlesome},
            {peevish}, {peckish}, {pettish}, {petulant}, {tetchy},
            {techy}]
     [also: {testiest}, {testier}]

testier
     See {testy}