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Pelas definições (técnicas) do termo "litmus test" diria : teste/experiência ou prova reveladora


-litmus test
1. Lit. a test used to determine the acidity or alkalinity of chemical substances. (Acid turns litmus paper red and alkaline compounds turn it blue.) I used a litmus test to show that the compound was slightly acid.
2. Fig. a question or experiment that seeks to determine the state of one important factor. His performance on the long exam served as a litmus test to determine whether he would go to college. The amount of white cells in my blood became the litmus test for diagnosing my disease.

-a litmus test
something that shows clearly what someone's opinions or intentions are
Usage notes: Litmus is a substance used in chemical tests because it changes colour.
His views on abortion are effectively a litmus test of his views on women's rights.