In my experience, they’re something that it’s fairly common for Christians to memorize, talk about, preach sermons on, etc. This is probably partly due to mankind’s instinctive love for Top Ten lists. Coming from the Old Testament, they’re not so much specifically Christian as Judeo-Christian.
A better “Christianity test” might be to recite the Lord’s Prayer (“Our Father…”).
Asimov has also written a reasonably famous essay about all four verses of TSSB; IIRC it originally appeared in his column in The Magazine of Fantasy and Science Fiction.
But Jesus wasn’t claiming he’d invented those commandments. He was citing existing commandments that he assumed his listeners were familiar with, and saying those were the most important of all the commandments.
Reform Jewish, I got all ten commandments, but put the ban on adultery in the wrong place – for some reason I always thought it was the 9th commandment.
I enjoy memorizing this kind of stuff. I also know and can sing all four verses of the Star Spangled Banner. During sporting events, I generally sing along using words from an alternate verse.
This was based on a series actual incidents, where Germany sent ~2500 troops pretending to be Americans in an attempt to capture a bridge and disrupt American operations. The questions caught some of the Germans, but also a decent number of Americans - there was an American Brigadeer general who spent hours at gunpoint because he got a question about the Cubs wrong.
Some Christians in 1980s told me that all non – Christians will suffer eternally. As a Jew I believe that Christians and Muslims who keep The Seven Commandments will be saved.