please i need help with this questions ? 1-Testing is intended to show that a program does what it is intended to do. Why may testers not always know...

please i need help with this questions ?

1-Testing is intended to show that a program does what it is intended to do. Why may testers not always know what a program is intended to do?  

2- What are the strategic options for legacy system evolution? When would you normally replace all or part of a system rather than continue maintenance of the software

3- Explain why it is reasonable to assume that the use of dependable processes will lead to the creation of dependable software

4- What are the significant benefits offered by the application system reuse approach over the custom software development approach?

5-How does the base application's design in the product line simplify reuse and reconfiguration?