I finally found out there's a name to a design pattern I've used previously.  The open closed principle: a class should be open for extension, but closed for modification. 

A co-worker was working a fairly complex presenter class that was originally difficult to test, had way to many responsibilities, and would need to be modified each time a new area of the application was completed.  After extensive refactoring it now is testable and passes the open closed principle.  Basically the presenter class was broken down into 6 other classes which implemented a strategy pattern.  Much more maintainable and easier to understand!