Unit tests

This is a level of testing that involves testing each unit that constitutes the components of a software application. This is the lowest level of test and it is done at the method or function level. It is primarily done by programmers, specifically to show code correctness and that the requirement has been correctly implemented. A unit test usually has one or more inputs and outputs.

It is the first level of test usually done in software development and it is designed to isolate units of software systems and test them independently or in isolation. Through unit testing, inherent issues and bugs in systems can be easily detected earlier in the development process.