Quality Code: Software Testing Principles, Practices, and Patterns

Becoming friend-ly

A relatively small number of languages have the equivalent of the C++ friend keyword. For example, Microsoft C# has the InternalsVisibleToAttribute class that can be used to grant access from specified contexts.

While many consider the friend keyword to be “dirty programming” and to violate principles of encapsulation,⁴ it is often cited as having positive value for testing purposes, especially unit testing. Consider a C++ implementation of a poker hand (Listing 9-10), in this case in a simple game of five-card stud. Of course, you do not want to reveal your cards to anyone else.

4. You can find a good discussion of this at www.cprogramming.com/tutorial/friends.html. Scott Meyers infers something similar when he says, “It ...