An empirical study on the adequacy of testing in open source projects

Abstract

Abstract—During software maintenance, testing is a crucial activity to ensure the quality of code as it evolves over time. With the increasing size and complexity of software, adequate software testing has become increasingly important. Code coverage is an important metric to gauge the effectiveness of test cases and the adequacy of testing. However, what is the coverage level exhibited by large-scale open-source projects? What is the correlation between software metrics and the code coverage of the software? In this study, we investigate the state-of-the-practice of testing by measuring code coverage in open-source software projects. We examine over 300 large open-source projects written in Java, to measure the code coverage of their associated test cases. We analyse correlations between code coverage and relevant software metrics such as lines of code, cyclomatic complexity, and number of developers. Our results show that the coverage level decreases with the increase in size and complexity of the software, whereas the number of developers has an insignificant correlation with the code coverage. However, considering individual files, coverage increases with the size and complexity, whereas the number of developers has no correlation with the code coverage. Our results highlight the strengths and weaknesses of testing in open-source projects and make recommendations for future research. Keywords—Code coverage, Software testing, Test adequacy, Software metric