4 (a) Creational and Structural are two design pattern categories. For each category, discuss an example pattern of your choice - in your answer give the intent and an example context where the pattern could be used. [2x6 Marks] (b) (i) Object oriented analysis and design models iteratively evolve from representations of system requirements. Technical reviews of these models are considered as important as final testing. Briefly discuss three aspects of these models that are of interest when undertaking reviews. [9 Marks] (ii) Outline what is meant by the terms Unit Testing and Test Driven Development (TDD) and discuss how a TDD approach utilising unit tests provides advantages over a more traditional approach. [12 Marks]