Migrating Unit Tests Across Java Applications

Writing effective unit tests is often tedious, difficult, and time-consuming. Test recommendation techniques facilitate this process by recommending existing manually written tests from other similar systems for developers to reuse. However, developers still have to put non-trivial effort into modifying the recommended tests. For example, they have to understand vari-ous code elements in the recommended tests to accurately replace them with semantically similar code elements from the target system. In this paper, we propose JTESTMIGRATOR, a technique to automatically migrate unit tests between semantically similar methods across applications. Given a source and a target method with similar functionality across applications, where the source method has some unit tests, JTESTMIGRATOR migrates unit tests by transforming the test code. JTESTMIGRATOR uses semantic similarity and type compatibility of code elements in the source and target systems to transform test code. We implement JTESTMIGRATOR to migrate JUnit tests and evaluate it on 104 tests for 42 methods across 5 popular libraries. JTESTMIGRATOR successfully migrates 76 (73%) of the tests for 32 (76%) of the methods across the 5 libraries. 10 (13%) of the successfully migrated tests increase the code coverage of 4 target methods.