There are basically 6 levels of Software Testing:--
a.In this level of testing small functions and modules of the project are tested.
c.Done by Developers.
a.In this level of testing small functions which make a module are tested.
b.Input------>Small Function+Small Function+Small Function------>Output.
c.Done by Team Lead.
a.In this level of testing all the modules which make a application are tested.
b.Done by Test Manager.
5)User Acceptance Testing:-
a.In the presence of customer conducting the testing known as User Acceptance Testing.
Before that we need to know couple of main definitions regarding the terminology in the company
PROJECT in which exact rules must be followed that is customer requirements
PRODUCT which are based on general requirements that is on our own requirements