Unit testing is a software development process in which the smallest testable parts of an application called units and are individually & independently scrutinized for proper operation. Unit testing is often automated but it can also be done manually. This testing mode is a component of Extreme Programming, a pragmatic method of a software development that takes a meticulous approach to building a product by means of a continual testing & revision

Unit testing involves only those characteristics that are vital to the performance of the unit under test. This encourages the developers to modify the source code without immediate concerns about how such changes might affect the functioning of other units or the program as a whole. Once all of the units in a program have been found to be working in the most efficient & error-free manner possible, larger components of the program can be evaluated by means of integration testing.

Unit testing can be time-consuming & tedious. It demands patience & thoroughness on the part of the development team. Rigorous documentation must be maintained. Unit testing must be done with an awareness that it may not be possible to test a unit for every input scenario that will occur when the program is run in a real-world environment.

Unit testing, a testing technique is using which individual modules are tested to determine if there are any issues by the developer himself. It is concerned with functional correctness of the standalone modules.

In procedural programming, a unit could be an entire module, but it is more commonly an individual function or procedure. In object-oriented programming, a unit is often an entire interface, such as a class, but could be an individual method.

Unit tests are short code fragments created by programmers or occasionally by white box testers during the development process. It forms the basis for component testing.