A unit test is a piece of code written and executed by software developers to ensure that a section of an application (known as a "unit") meets its design and behaves as intended.

A unit can be almost anything you want it to be, from just line of code, a method, or a class. However in general, smaller is better since smaller tests give you a much more granular view of how your code is performing.

The goal of unit testing is to isolate each part of the program and show that the individual parts are correct, as a result it provides two main advantages:

• Finds problems early in the development cycle
• Allows the programmer to refactor code or make upgrades and make sure the module still works correctly