We are investigating how to use new logging tools for Java programs to automatically generate regression test data and regression tests for productive systems. This is intended to minimize the risk and effort involved in refactoring software. The key points of the project are: 1. Performance influence: The use of the logging systems in productive programs is only possible if the functionality and stability are not affected too much. We will investigate which performance effects the various tools produce and develop criteria for when and where they can be used - and when not. 2. Test data generation: The logging function allows you to know which methods are called for productive operation and with which input and output values. For efficient regression testing, parts of the system (external services, databases, etc.) must be moxed. We will investigate how to automatically create equivalence classes and how to automatically generate suitable test cases and mock objects from the logging data. 3. Implementation 3: We will implement a tool that can automatically generate and execute appropriate regression tests.