acid test

English

From the testing of gold with nitric acid (true gold is not affected).

acid test (plural acid tests)

(figuratively) A rigorous test or appraisal of the quality or worth of something.
- 2020 May 20, Stefanie Foster, “Comment: Safety first: now more than ever”, in Rail, page 3:
  The acid test: will the British public abide by such stringent guidelines about where they should stand, walk or sit in our stations and on our trains, when they have been used to a turn-up-and-go railway where they enjoyed freedom having bought their ticket?
- 2021 July 7, Phil McNulty, “England 2-1 Denmark”, in BBC Sport‎:
  This was the acid test - at least before Sunday's final with formidable Italy - and they came up with the goods not only in the context of Euro 2020 but also in demonstrating their character and big match mentality.
(historical) In the 1960s, a party based around the use and advocacy of the psychedelic drug LSD ("acid").

Rigorous test or appraisal of the quality or worth

Arabic: please add this translation if you can
Chinese:
Cantonese: 洗禮 (sai² lai⁵)
Mandarin: 決定性考驗／决定性考验 (juédìngxìng kǎoyàn), 洗禮洗礼／洗礼洗礼 (zh) (sǐlǐ)
Finnish: happotesti
French: épreuve par le feu (fr)
German: Lackmustest (de)
Greek: λυδία λίθος (el) f (lydía líthos), βάσανος (el) f (vásanos)
Irish: promhadh an aigéid m
Italian: banco di prova (it) m
Romanian: probă de foc
Russian: please add this translation if you can
Spanish: prueba de fuego, prueba del algodón f