It follows the Single Responsibility principle giving a class no more than one reason to change (the data changes).

This isolation supports the Single responsibility principle.

The single responsibility principle says that these two aspects of the problem are really two separate responsibilities, and should therefore be in separate classes or modules.

The decorator pattern is often useful for adhering to the Single Responsibility Principle, as it allows functionality to be divided between classes with unique areas of concern.

Dependency injection separates the creation of a client's dependencies from the client's behavior, which allows program designs to be loosely coupled and to follow the dependency inversion and single responsibility principles.

The single responsibility principle states that every module or class should have responsibility over a single part of the functionality provided by the software, and that responsibility should be entirely encapsulated by the class.

This, however, introduces unnecessary coupling between tests and breaks the Single responsibility principle, which, states that every context (class, function, variable, etc.) should define a single responsibility, and that responsibility should be entirely encapsulated by the context.