The Software Product Lines (SPL) approach requires specific testing tools that should help to manage reusable testing assets and automate the test execution. Despite of the increasing interest by the research community regarding software testing tools, SPL still need tools to support the testing process. This book presents the results of a mapping study on software testing tool and defines the requirements, design and implementation of a software product lines system testing tool, aiming at the creation and management of test assets. A controlled experiment and replications were also conducted to evaluate the tool effectiveness.