Automatic Generation of Unit Regression Tests

Software developers spend a significant amount of time modify- ing existing code. Regression testing (comparing previous behav- ior with current behavior) can be a powerful technique to check that modifications do not introduce unintended changes. This pa- per introduces a technique to automatically create class-specific regression tests from a program run. The technique is implemented for the Java language in Palulu. In order to test a class, it may be necessary to place the class and other classes that it depends upon in specific states. To get to the desired state, methods may be need to be called in a particular order and with specific parameters. Palulu uses information from the program run to accomplish this. It builds a model for each class and uses the model to explore the possible behaviors of the class and build corresponding regression tests. It usesobserver methods (those that do not modify the state) to capture the result. In our experiments, Palulu succeeded in building tests for non- trivial programs and performed as well as or better than hand written tests.