Play to Grade: Testing Coding Games as Classifying Markov Decision Process
This addresses the challenge of providing feedback for interactive programs in coding education, offering a novel solution for educators and students.
The paper tackles the problem of automatically grading interactive coding assignments, which are impossible to grade with traditional unit tests, by formalizing it as classifying Markov Decision Processes (MDPs) and achieves an automatic feedback system with a dataset of 711,274 student submissions.
Contemporary coding education often presents students with the task of developing programs that have user interaction and complex dynamic systems, such as mouse based games. While pedagogically compelling, there are no contemporary autonomous methods for providing feedback. Notably, interactive programs are impossible to grade by traditional unit tests. In this paper we formalize the challenge of providing feedback to interactive programs as a task of classifying Markov Decision Processes (MDPs). Each student's program fully specifies an MDP where the agent needs to operate and decide, under reasonable generalization, if the dynamics and reward model of the input MDP should be categorized as correct or broken. We demonstrate that by designing a cooperative objective between an agent and an autoregressive model, we can use the agent to sample differential trajectories from the input MDP that allows a classifier to determine membership: Play to Grade. Our method enables an automatic feedback system for interactive code assignments. We release a dataset of 711,274 anonymized student submissions to a single assignment with hand-coded bug labels to support future research.