A Test-Driven Approach to Improving Student Contributions to Open-Source Projects

Test-driven development (TDD) promises to help students write high-quality code with fewer defects. Although many studies of TDD usage have been conducted in entry-level computer science courses, few have looked at more advanced students doing projects of larger scope, such as contributing to open-source software (OSS). To test the performance of the test-driven approach on OSS-based course projects, we conducted a quasi-experimental controlled study, which lasted for more than one month. Thirty-five masters students participated in our study. They worked on course projects in teams, half of which were assigned to the TDD group (using a test-driven approach), and the rest of which were assigned to the non-TDD group (using the traditional test-last approach). We found that students in the TDD group were able to apply test-driven techniques pragmatically-spending more than 20% of their time on average complying with the test-driven process-throughout the whole project. There were no major differences in the quality of source-code modifications and newly added tests between the TDD group and the non-TDD group; however, the TDD group wrote more tests and achieved significantly higher (12% more) statement coverage.