SQA Engineer Question:

The hierarchical approach is at the heart of the object-oriented testing system. This test approach uses and builds upon several well-understood testing techniques, tying them together into a comprehensive testing system. The hierarchical approach leverages the fact that "everything is a system." It defines and applies testing standards for several levels of software component: objects, classes, foundation components, and systems. The hierarchical approach designates as SAFE those components that meet the testing standards for that kind of component. Once you designate a component as SAFE, you can integrate it with other SAFE components to produce the next-level component. In turn, you test this component to the level of safety
associated with the component level it represents. SAFE is always a relative state. It depends entirely on the standards you choose to enforce, your application, your attitude toward risk, and the specific risks and risk management practices you adopt in your project. The hierarchical approach provides guidelines for minimum safety; you decide what is right for you.