[yorwba]

You could make the pre-quiz part of the "immediate satisfaction" by calibrating the questions so that the learner can feel good about their current knowledge without making them spend a long time solving difficult problems. Making a quiz fun is probably easier than doing the same for the actual learning part, which might require much more time before seeing any satisfying results.

Another way to assess knowledge would be to give the learner topics of varying difficulty to select from; it's unlikely that they'd choose something so easy that it'd be boring and in case the topic is too hard, there should be an escape route to something easier.