Quality Code: Software Testing Principles, Practices, and Patterns

Use Existing No-Op Classes

In my opinion, one of the most underutilized of the common design patterns is the Null Object pattern.³ The concept is simple. Instead of returning the ubiquitous null (or its various equivalents such as undef, nil, or NULL) and testing for it as a special value, we return an object of the expected type that implements the behavior associated with an unknown, missing, or indistinct value. Several such objects may reasonably exist for a given situation, giving rise to Martin Fowler’s Special Case pattern⁴ as a generalization.

3. Surprisingly to many, this is not one of the original Gang of Four design patterns but was first proposed in the Pattern Languages of Program Design series. Martin Fowler [REF], Josh Kerievsky ...