An acid test, when used as an idiom, is a situation or event that provides definitive proof of whether something is true or false, right or wrong, good or bad, effective or ineffective. This does not have to be an actual ‘test’ but can be anything which provides such conclusive confirmation. Quite often, the expression is used to refer to something which confirms a person’s character or ability.
The term is sometimes used more specifically in business as in the ‘acid test ratio’ which determines a business’ liquidity by examining its cash, accounts receivable, and trading securities. Another variation of this idiom is “Litmus test.”
Origin of “Acid Test”
The idiom acid test comes from tests used to check the fineness or purity of gold since gold is resistant to acid. This test figured prominently in the fortunes of the ’49’rs’ who flocked to the California Gold Rush of 1849, but test didn’t enter the language as a common idiom until the 1900’s.
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Sentence Examples
“He appears to be ready for management, but the acid test will be how he handles this production shortfall.”
“My knee has been fine in training but tomorrow’s game will be the acid test.”
“This is the acid test of stamina and endurance. The Tour de France has always been a brutal event.” — The Armstrong Lie (2013)
“Lisbon is filled with men much more attractive than you.” “It’s the acid test. If she keeps her promise to return, I’ll never be afraid again of losing her.” — Reunion in France (1942)
“Oh, pulled a coin out of her ear, she didn’t even laugh. There’s something wrong with that girl. That is the acid test. — Smile (2006)