Unit testing is used to check basis functionality and behavior of the smallest and independent part (function, method or etc.) of the code blocks that performs certain operations. In modern software development approaches, unit testing plays a key-role because unit tests directly affects code quality. On the other hand, when we look at unit testing in terms of continuous integration and continuous development approach, the entire application code can be tested before the production deployment process with help of unit test methods. If any unit test returns fail, we can automatically cancel the deployment process.