acid test
n.
A decisive trial to determine worth or quality, as in Exposure to brilliant sunlight is the acid test for showing this fabric won't fade. Alluding to a 19th-century chemical test for distinguishing gold from other metals, this term was used figuratively by the early 1900s
Ok, sharpen your pencils. I'm now accepting proposals for an acid test for Orthodox Judaism. Youyr entry should be in the form of a "yes" or "no" question. Have fun. And I mean that.