The anticipated test design and its use in legacy code refactoring: Lessons learned from a real experiment

The maintenance of legacy code is a hard task since developers do not have access to details of its implementation. Thus, the refactoring of code units usually generates problems in other parts of the code that already had been validated. A solution to this problem is to use an anticipated test design methodology, where unit tests are first created to each module/class/methods before their modification. Thus, developers are able to ensure the correct performance of functions after their refactoring. This work discusses our experience in applying this methodology to the Data Access Object (DAO) layer refactoring of a real legacy application of a mobile multinational. Our results show that this strategy assists developers in better understanding the code and improves the performance of unit tests since they are produced by the own development team. Furthermore, we show the importance of the miniworld definition, which tries to represent a set of data that increases the coverage of the test process.