Preprint of paper published in: 16th European Conference on Software Maintenance and Reengineering (CSMR), 27-30 March 2012; doi:10.1109/CSMR.2012.12 Unit and integration tests can be invaluable during software maintenance as they help to understand pieces of code, they help with quality assurance and they build up confidence amongst developers. Unfortunately then, previous research has shown that unit tests do not always co-evolve nicely with the production code, thus leaving the software vulnerable. This paper presents TestNForce, a tool that helps developers to identify the unit tests that need to be altered and executed after a code change, thereby reducing the effort needed to keep the unit tests in sync with the changes to the production code. In order to evaluate TestNForce, we perform a user study that evaluates the adequacy, usefulness and completeness of TestNForce.