litmus test

plural litmus tests

1. chemistryA simple, binary test for the acidity or alkalinity of a substance, using litmus paper.
2. broadlyfigurativelyAny test which produces a binary, decisive result (for example, determining whether to appoint someone to a job) by measuring a single indicator.

   Exams, not interviews, have become the litmus test for entry to university.

   5 more examples

   Temple, under its new coach, Ray Morrison, formerly of Vanderbilt, will be put to the blue litmus test Friday night when it takes on Georgetown.

   1940 October 2, Allison Danzig, “Leading Elevens Face Stern Threats in Saturday's Games”, in New York Times, page 27

   For good reasons or bad, early membership of the currency union has become the litmus test of being a "good European."

   1998 February 16, “Baby-Boomer Bonding”, in Newsweek

   He opposes a constitutional amendment to ban same-sex marriage—a litmus test for many social conservatives

   2004 November 15, Matthew Cooper, “Candidates In the Wings”, in Time, archived from the original on 20 Feb 2013

   For years, quoting lines from “Manhattan” or another film by Mr. Allen on a date could be a romantic litmus test, a way to find out if a potential partner also loved E. E. Cummings, Paris, 1930s jazz and the sophisticated, cultured world the films often came to represent.

   2018 March 1, Steven Kurutz, quoting Lisa Schwarzbaum, “How Do You Solve a Problem Like ‘Manhattan’?”, in The New York Times, →ISSN

   "[…] I don't know National Rail numbers, but I do know that after the pandemic I used to go round a lot of the London stations, and they had far more locations shut than I did at St Pancras. That was very much my litmus test."

   2024 January 24, Dyan Perry talks to Nick Brodrick, “The industry has given me so much”, in RAIL, number 1001, page 44