This paper discusses the development of a source evaluation assessment, and presents the results of using this instrument in a one-semester information literacy course for journalism students. The assessment was developed using the threshold concept perspective, the "authority is constructed and contextual" frame, and an established source evaluation rubric. As formative assessment, the instrument showed that students' source evaluations lacked evidence and included ritualized language. As summative assessment, it showed that students used a greater range of indicators of authority than they used initially, and used evidence more frequently. The assessment can measure students' source evaluations across the disciplines.