小试牛刀

to give a small demonstration of one's impressive skills (idiom)

small / tiny / few / young

to test / to try / experiment / examination / test

ox / cow / bull / CL:條|条[tiao2],頭|头[tou2] / newton (abbr. for 牛頓|牛顿[niu2 dun4]) / (slang) awesome

knife / blade / single-edged sword / cutlass / CL:把[ba3] / (slang) dollar (loanword) / classifier for sets of one hundred sheets (of paper) / classifier for knife cuts or stabs