At this level we conduct Unit Testing. Considering the process from the procedural point of view, testing within the context of software engineering is actually a series of four steps that are implemented sequentially. Initially, tests focus on each module individually, assuring that it functions properly as a unit. Hence, the name Unit Testing. Unit testing makes heavy use of white-box testing techniques, exercising specific paths in a module's control structure to ensure complete coverage and maximum error detection.
Unit testing focuses verification effort on the smallest unit of software design the module.
The unit test is normally white-box oriented, and the step can be conducted in parallel for multiple modules. The product should be properly packaged, labeled, and include user manual.