This part of the book discusses two specialized aspects of testing. Chapter 11 discusses testing of object oriented systems. We discuss here how the types of tests discussed in the previous parts have to be adapted to fit into the needs of object oriented systems. The other chapter in this part, Chapter 12, discusses usability and accessibility testing. This is becoming increasingly important to meet the nebulous user interface expectations of users and also because legal frameworks are demanding that products be fit for use by people with physical challenges.