Summative assessment is a dead duck. We all know this. Aside from a final examination, all of the assessment we do these days should be formative. It should enable the student to improve. Yet still we use written tests which give students a score, a grade or percentage. Now, of course a student can self-reflect on why they got the grade they did or the teacher can go through the test paper explaining errors but to do this on an individual, rather than whole-class basis is almost impossible. How then does a teacher give rich and detailed feedback to their students without it being a huge increase in workload? The answer is diagnostic testing, a technique which allows formative feedback to be generated from summative feedback.