While the benefits and importance of formative assessment are well known, it can be challenging to incorporate formative assessment in large class teaching. This paper outlines how technology can be used to provide engaging, beneficial formative assessment for two cohorts of computer science students (n=138; 170). It provides an overview of the role of self-tests for students as an integral part of learning. They provide immediate feedback to students and also to the lecturer in what areas students need extra support. They are also a useful preparation tool for students in advance of assessment that contributes to their final mark. Student engagement with the self-tests is good, once they know they are available and there are no negative consequences for low scores. The upfront effort required to develop 100 and 150 words briefly specifying the focus and aims, the key findings and the implications or conclusions drawn.