As of June 2021, FAA Form 7711-1, U.S.C. 44809 “Exception for Limited Recreational Operations of Unmanned Aircraft” makes it a requirement for all U.A.S. pilots (except part 107 certified U.A.S. pilots) to take and pass the TRUST (The Recreational UAS Safety Test) exam.
Proof of the passed exam and FAA registration of the U.A.S. pilot must be available when requested by an officer of the law or an FAA representative.
The TRUST exam can be found at The Recreational UAS Safety Test (TRUST) | THE RECREATIONAL UAS SAFETY TEST (TRUST) TEST by AMA (modelaircraft.org)