Product line processes still lack support for testing end-product functions by taking advantage of the specific features of a product line (commonality and variabilities). Indeed, classical testing approaches cannot be directly applied on each product since, due to the potentially huge number of products, the testing task would be far too long and expensive. There is thus a need for testing methods, adapted to the product line context, that allow reducing the testing cost. The approach we present is based on the automation of the generation of application system tests, for any chosen product, from the system requirements of a product line. These PL requirements are modeled using enhanced UML use cases which are the basis for the test generation. Product-specific test objectives, test scenarios, and test cases are successively tional variation points at requirement level to automatically generate the behaviors specific to any chosen product. With such a strategy, the designer may apply any method to produce the domain models of the product line and then instantiate a given product: the test cases check that the expected functionalities have been correctly implemented. The approach is adaptive and provides automated test generation for a new product as well as guided test generation support to validate the evolution of a given product.