Detecting and addressing design smells in novice Processing programs

Many novice programmers are able to write code that solves a given problem, but they struggled to write code that adheres to basic principles of good application design. Their programs will contain several design smells which indicate a lack of understanding of how to structure code. This applies in particular to degrees in which programming, and by extension software design, is only a small part of the curriculum.

This paper defines design smells for Processing, a language for new media and visual arts that is based on Java. This includes language specific smells that arise from the common structure that all Processing programs share. The paper also describes how to detect those smells automatically with static analysis. This tool is meant to support teaching staff with providing feedback to novices on program design.

We applied the tool to a large set of student programs, as well as programs from the Processing community, and code examples used by textbooks and instructors. The latter gave a good sense of the quality of resources that students use for reference. We found that a surprising number of resources contains at least some design smell. The paper then describes how to refactor the code to avoid these smells. These guidelines are meant to be practical and fitting the concepts and constructs that are known to first-year students.