Collaborative systems are widely used today in various activity fields. Their complexity is high and the development involves numerous resources and costs. Testing collaborative systems has a very important role for the systems' success. In this paper we present taxonomy of collaborative systems. The collaborative systems are classified in many categories and there are a lot of criteria for collaborative systems classification. It is presented the importance of testing process in collaborative systems. The paper presents methods, techniques and builds metrics for collaborative systems testing, focusing on collaborative software. (Contains 4 figures, 1 table, and 4 endnotes.)