Software reuse was focused for the way of improving programmer productivity from the crisis of software. Object oriented technology impact on overall area of software engineering, such as software analysis , Programming language. testing and maintenance. The new concepts, Class, Inheritance and encapsulation, not only introduce new testing problems and they raise a new challenging question of how to conduct regression testing for 0-0 programs the first problem of regression testing is how to identify the affected components due to the changes of some components. We propose a method firewall to enclose all classes and methods affected by the changes to one or more methods in Inheritance relation