The rising use of technology in classrooms has also brought with it a concomitant wave of computer-based assessments. The argument for computer-based testing is often framed in terms of efficiency and data management: computer-based tests facilitate more efficient processing of test data and the rate at which feedback can be leveraged for student learning rather than being framed in terms of the direct effects that students experience from engaging with novel learning tools. Whilst potentially beneficial, for some students the outcomes of computer-based tests may be counter-productive. This review considers the cognitive, and often implicit, consequences of testing mode upon students with reference to testing performance and subjective measures of cognitive load. Considerations for teachers, test writers and future research are presented with a view to raising the significance of learners' subjective experiences as a guiding perspective in educational policy making.