[테스트 주도 개발](/pages/Test-driven%20development.txt)의 [리팩토링](/pages/Refactoring.txt) 패턴 중 하나. 변화를 가하기 전에 해당 영역을 분리하기.

> How do you change one part of a multi-part method or object? First, isolate the part that has to change. The picture that comes to my mind is surgery: The entire patient except the part to be operated on is draped. The draping leaves the surgeon with only a fixed set of variables. …
>
> Some possible ways to isolate change are <Extract method> (the most common), Extract object, and Method object.
>
> --Chapter 31, [Test-driven development: by example](/pages/publications/Test-driven%20development%20-%20By%20example.txt)