Design Pattern Density and Design Maturity

JUnit is a widely-adopted unit testing framework for Java, developed by Kent Beck and Erich Gamma. In their discussion of JUnit 3.8’s design, the authors state:

Notice how TestCase, the central abstraction in the framework, is involved in four patterns. Pictures of mature object designs show this same ‘pattern density’. The star of the design has a rich set of relationships with the supporting players.

The notion of design pattern density has been around forever, but with little serious work being done to refine the idea. I’m calling on all experts (reading this blog…) to tell me whether they agree or disagree with the following statement:

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