An overview of the evolution of the concept of testor

In this paper, the historical evolution of the concept of testor is presented. Testors in a bivalued logic, in a k-valued logic, and also in a fuzzy logic are considered, particular considerations about each case are expressed. This concept evolution is presented to English readers for the first time. The authors reviewed this history because testor, in each particular formulation, is an interesting tool for feature selection problems, especially when the descriptions of objects are non-classical.