This is the replication package for the paper "Enhancing Genetic Improvement of Software with Regression Test Selection", accepted at ICSE 2021.The data is 360MB compressed and around 1GB uncompressed.The full package contains: tool used to run the experiments, subject programs, data analysis scripts, and resulting data from our experiments. Moreover, we provide .md files with guides on how to setup and run the experiments.In order to run the experiments, you will need Java 8 installed. In order to analyse the experiments, you will need R installed. More details can be found in "REQUIREMENTS.md".More information can be found in the "README.md" file included in this package.