Kinh nghiệm - Thủ thuật

One of the most beneficial features of object-oriented development is encapsulation. This is a technique that can be used to hide information. A program unit, in this case a class, can be built with a well-defined public interface that proclaims its services (available methods) to client classes. The implementation of the services is private. Clients who use the services are unaware of implementation details. As long as the interface is unchanged, making changes to the implementation should not affect the client classes. A tester of object-oriented code would therefore conclude

that only the class with implementation changes to its methods needs to be retested. Client classes using unchanged interfaces need not be retested. This is not necessarily correct, as Perry and Kaiser explain in their paper on adequate testing for object-oriented systems. In an object-oriented system, if a developer changes a class implementation that class needs to be retested as well as all the classes that depend on it. If a superclass, for

example, is changed, then it is necessary to retest all of its subclasses. In addition, when a new subclass is added (or modified), we must also retest the methods inherited from each of its ancestor superclasses. The new (or changed) subclass introduces an unexpected form of dependency because there now exists a new context for the inherited components.