The present study investigated the usefulness of a pre-programmed, teleoperated, socially assistive peer robot in dynamic testing of complex problem solving utilising the Tower of Hanoi. The robot, in a 'Wizard of Oz' setting, provided instructions and prompts during dynamic testing to children when they had to solve 3 D Tower of Hanoi puzzles. Participants were 37 second grade 8-year-old children, of whom half received graduated prompts training between pre-test and post-test, delivered by the robot, and half did not. It was found that children's progression in task accuracy varied considerably, depending on whether or not children were trained in solving Tower puzzles. Trained children showed greater progression in the number of Tower problems that they could solve accurately, made considerably fewer steps, although the Tower puzzles increased quickly in difficulty level. The mean completion time of trained children decreased at a slower rate than that of the untrained children, but both groups of children took considerably more time to think and plan ahead before they started the solving process. Only moderate relations with planning behaviour were found. In general, the study revealed that computerised dynamic testing with a robot as assistant has much potential in unveiling children's potential for learning and their ways of tackling complex problems. The advantages and challenges of using a robot in educational assessment were discussed.