Separation of interface from implementation

Separation of interface from implementation is an important concept in unit testing. The interface of a component defines the set of inputs and outputs that the component provides to the rest of the system. The implementation, on the other hand, is the internal code that performs the actual processing.

In unit testing, it is important to test only the interface of a component, and not its implementation. This is because testing the implementation may result in tests that are tightly coupled to the implementation details, making it difficult to refactor or modify the code in the future. Additionally, testing the implementation may result in tests that are brittle and difficult to maintain.

By separating the interface from the implementation, unit tests can be written to test the functionality of the component in isolation, without requiring knowledge of the internal implementation. This approach allows tests to be written that are more flexible, maintainable, and resistant to changes in the implementation details.

One common technique for separating the interface from the implementation is to use mock objects. A mock object is a placeholder object that mimics the behavior of a real object, but provides a simplified, predictable interface. By using mock objects, developers can test the behavior of a component without relying on the implementation details of other components. Overall, the separation of interface from implementation is an important concept in unit testing. By testing only the interface of a component, developers can write tests that are more flexible, maintainable, and resistant to changes in the implementation details. This approach can help to improve the overall quality, reliability, and maintainability of the software.