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
