The CQL expression was compiled just fine but seems to be not testable in Bonnie. I have created a testing patient with Payer = Medicare with FFS code (i.e. 121) (see attached screenshot). If I removed the where clause from the query below, then the test case was passed. Can you please let me know if I missed any thing when creating the testing patient? Thank you very much for your help. Regards, Tien Thai ========================================= code "Medicare FFS": '121' from "SOP" display 'Medicare FFS' define "Was Active Medicare FFS Beneficary At The Time Of The Procedure": ["Participation": "Medicare payer"] MedicareFFSBen with ["Procedure, Performed"] ProcedureDate such that MedicareFFSBen.participationPeriod overlaps ProcedureDate.relevantPeriod where MedicareFFSBen.code = "Medicare FFS"