Endorsement test
The endorsement test was proposed by Sandra Day O'Connor, a member of the United States Supreme Court. She suggested it in her judgment in a lawsuit called Lynch v. Donnelly in 1984.
The endorsement test is a question that you can ask if you think that the government is doing something in favor of religion. According to the United States Constitution, the government cannot endorse any particular religion, and cannot endorse religion in general. The test asks: is the government doing something that makes people think that the government endorses religion? If so, that government act may not be allowed under the Constitution.