What is Unit testing?

• Unit testing is a method by which individual units of source code are tested to determine if they are fit for use. A unit is the smallest testable part of an application like functions/procedures, classes, interfaces.
• Unit tests are typically written and run by software developers to ensure that code meets its design and behaves as intended.
• The goal of unit testing is to isolate each part of the program and show that the individual parts are correct.
• A unit test provides a strict, written contract that the piece of code must satisfy. As a result, it affords several benefits. Unit tests find problems early in the development cycle.