litmus test

A litmus test is like a quiz to help decide whether something is good or bad. It's like being asked a few questions, and depending on how you answer them, it will determine if the thing is true or not. For example, if you are voting for a candidate for president, you could have a litmus test that includes questions about their positions on topics like the economy or healthcare. If the candidate passes the litmus test, then it means they are a good choice for president.