Usage of Tests in an Open-Source Community

International audienceDuring the development, it is known that tests ensure the good behavior of applications and improve their quality. We studied developers testing behavior inside the Pharo community in the purpose to improve it. In this paper, we take inspiration from a paper of the literature to enhance our comprehension of test habits in our open source community. We report results of a field study on how often the developers use tests in their daily practice, whether they make use of tests selection and why they do. Results are strengthened by interviews with developers involved in the study. The main findings are that developers run tests every modifications of their code they did; most of the time they practice test selection (instead of launching an entire test suite); however they are not accurate in their selection; they change their selection depending on the duration of the tests and; contrary to expectation, test selection is not influenced by the size of the test suite