What is unit testing

Testing of individual units or groups of related code is known as Unit Testing.Unit tested with a Unit Test Plan (UTP)

           Unit testing is testing of smallest testable part of the software. It can be an individual program or a group of programs, forming a unit. The definition of  ‘unit’ can be left to the project team. In some cases one single program can be considered as a unit or in some other cases, a set of related programs can be considered as a
unit. This discretion can be left to individual project teams. In some cases it is also referred as component
testing.

             It is very important that unit testing needs to be carried out with a help of a unit test plan. Note that this unit test plan should have been prepared during the detail design stage and not after coding! The reason behind it is that if you prepare a unit test plan based on your code, any defect in the code will creep into the unit test plan too defeating the very purpose of unit testing