What indicator do you use to plan time for retesting code changes during a project?

To plan time for retesting code changes during a project, I typically use the "bug density" metric, which measures the number of defects relative to the size of the codebase. Additionally, I consider the complexity of the changes made, as more complex modifications often require more extensive retesting. Historical data on previous cycles can also inform estimations, allowing for a more accurate allocation of time for retesting. Finally, collaboration with the QA team helps ensure that adequate time is set aside based on their insights and testing needs.