Abstract. Software Product Line (SPL) engineering offers several advantages in the development of families of software products. There is still a need, however, for better understanding of testability issues and for testing techniques that can operate cost-effectively on SPLs. In this paper we consider these testability issues and highlight some differences between optional versus alternative features. We then provide a graph based testing approach called the FIG Basis Path method that selects products and features for testing based on a feature dependency graph. We conduct a case study on several non-trivial SPLs and show that for these subjects, the FIG Basis Path method is as effective as testing all products, but tests no more than 24% of the products in the SPL.