Using Fine-Grained Test Cases for Improving Novice Program Fault Localization

Online Judge (OJ) system, which can automatically evaluate the results (right or wrong) of programs by executing them on standard test cases, is widely used in programming education. While an OJ system with personalized feedback can not only give execution results, but also provide information to assist students in locating their problems quickly. Automatically fault localization techniques are designed to find the exact faults in programs automatically, experimental results showed their effect on locating artificial faults, but their effectiveness on novice programs needs to be investigated. In this paper, we first evaluate the effectiveness of several widely-studied fault localization techniques on novice programs, and then we use fine-grained test cases to improve the fault localization accuracy. Empirical studies are conducted on 77 real student programs and the results show that, compared with original test cases in OJ system, the fault localization accuracy can be improved obviously when using fine-grained test cases. More specifically, in terms of TOP-1, TOP-3 and TOP-5 metrics, the maximum results can be improved from 5, 22, 37 to 9, 24, 48, respectively. The results indicate that more faults can be located when checking the top 1, 3 or 5 statements, so the fault localization accuracy is enhanced. Furthermore, a Test Case Granularity (TCG) concept is introduced to describe fine-grained test cases, and empirically studies demonstrate that there is a strong correlation between TCG and fault localization accuracy.