What is unit testing?

Unit testing is a type of software testing where individual units or components of a software are tested. The purpose is to validate that each unit of the software performs as designed. A unit is the smallest testable part of any software and typically has one or a few inputs and usually a single output. Unit testing is done during the development (coding phase) of an application by the developers. Unit tests isolate a section of code and verify its correctness. A well-written unit test case is independent of other units. This testing method is often automated but can also be done manually. Frameworks such as JUnit (for Java), NUnit (for .NET), and others facilitate the testing process by providing a structured way to create and run tests.

Unit testing has several key benefits:

1. Early Problem Detection: Bugs can be found and fixed early in the development cycle, saving time and effort in later stages of development.
2. Facilitates Changes: Having a suite of unit tests makes it safer and easier to refactor code or upgrade system libraries, as changes can be verified quickly to ensure no existing functionality is broken.
3. Simplifies Integration: Unit testing helps in simplifying the integration process, as problems are more likely to be caught at the unit level.
4. Documentation: Unit tests can serve as documentation of the system. They can help new team members understand the base functionality of the unit without going through the code in detail.
5. Design: Writing unit tests