acid test
noun /ˌæsɪd ˈtest/
/ˌæsɪd ˈtest/
(also litmus test)
[singular]- a way of deciding whether something is successful or true
- The acid test of a good driver is whether he or she remains calm in an emergency.
- The perception of fairness is the acid test for democracy.
- This type of stone is the acid test of a climber’s ability.
Word Originfiguratively, from the original use which was a test for gold using nitric acid.