This paper presents PLUTO, a simple and intuitive methodology to manage the testing process of product lines, described as Product Lines Use Cases (PLUCs). PLUCs are an extension of the well-known Cockburn’s Use Cases, a notation based on natural language descriptions of requirements. The proposed test methodology is based on the Category Partition method, and can be used to derive a generic Test Specification for the product line, and a set of relevant test scenarios for a customer specific application. Categories and Subject Descriptors D.2.1 [Software]: Requirements/Specifications. D.2.5 [Software]: Testing and Debugging - Testing tools (e.g., data generators, coverage testing). General Terms Verification. Keywords Product Lines, Use Cases, Black box testing.