What are the Testing Habits of Developers? A Case Study in a Large IT Company

Tests are considered important to ensure the good behavior of applications and improve their quality. But development in companies also involves tight schedules, old habits, less-trained developers, or practical difficulties such as creating a test database. As a result, good testing practices are not always used as often as one might wish. With a major IT company, we are engaged in a project to understand developers testing behavior, and whether it can be improved. Some ideas are to promote testing by reducing test session length, or by running automatically tests behind the scene and send warnings to developers about the failing ones. Reports on developers testing habits in the literature focus on highly distributed open-source projects, or involve students programmers. As such they might not apply to our industrial, closed source, context. In this paper, we take inspiration from experiments of two papers of the literature to enhance our comprehension of the industrial environment. We report the 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 reinforced by interviews with developers involved in the study. The main findings are that test practice is in better shape than we expected; developers select tests "ruthlessly" (instead of launching an entire test suite); although they are not accurate in their selection, and; contrary to expectation, test selection is not influenced by the size of the test suite nor the duration of the tests.