To learn how to introduce automated regression testing to existing medium scale Open Source projects, a long-term field experiment was performed with the Open Source project FreeCol. Results indicate that (1) introducing testing is both beneficial for the project and feasible for an outside innovator, (2) testing can enhance communication between developers, (3) signaling is important for engaging the project participants to fill a newly vacant position left by a withdrawal of the innovator. Five prescriptive strategies are extracted for the innovator and two conjectures offered about the ability of an Open Source project to learn about innovations.
