Common Bugs in Scratch Programs

Abstract

Bugs in Scratch programs can spoil the fun and inhibit learning success. Many common bugs are the result of recurring patterns of bad code. In this paper we present a collection of common code patterns that typically hint at bugs in Scratch programs, and the LitterBox tool which can automatically detect them. We empirically evaluate how frequently these patterns occur, and how severe their consequences usually are. While fixing bugs inevitably is part of learning, the possibility to identify the bugs automatically provides the potential to support learners. CCS CONCEPTS• Social and professional topics → Software engineering education; K-12 education; • Software and its engineering → Visual languages.

Finding Anomalies in Scratch Assignments

“…Our tool chain for anomaly detection for SCRATCH uses an extended version of Li t t e r Bo x [10] to generate a collection (mi , . .…”

“…We therefore conducted a sensitivity analysis on these two parameters with minimum size (= 2) and maximum deviation level (= 10000) as fixed variables, changing only minimum support and minimum confidence. For the minimum support we tested the values (1,5,10,15,20), where 20 is the default JADET value. For confidence we tested the values ( 0 .…”

“…• Bug pattern (defective): The violation hints at a defect that a generic SCRATCH linter such as Lit t e r Bo x [10] could find equally well.…”

“…It has been shown that various types of code smells are prevalent [1], [17], [36], [40] and have a negative impact on code understanding [16]. There are tools for finding code smells in Sc r a t c h programs such as Ha ir b a l l [5], Qu a l it y h o u n d [40] or SAT [6], and Li t t e r Bo x [10] detects predefined bug patterns automatically.…”

“…We implemented our approach as an extension of Lit t e r -Bo x [10] and JADET [42], [44] and it is available at: https://github.com/se2p/scratch-anomalies…”