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Evidence suggests that as software ages the original realizations of design patterns remain in place, and participants in design pattern realizations accumulate "grime" - non-pattern-related code. This research examines the consequences that grime buildup has on the testability of general purpose design patterns. Test cases put in place during the design phase and initial implementation of a project can become ineffective as the system matures. The evolution of a design due to added functionality or defect fixing increases the coupling and dependencies between many classes that must be tested. We show that as systems age, the growth of grime and the appearance of anti-patterns increase testing requirements. Early recognition and removal of grime and anti-patterns can potentially improve system testability.