What are the benefits of unit testing?

• Early identification of the defects in SDLC helps to save money and time - When testers do not find mistakes early, It becomes more expensive as product comes closer to the release. Unit testing helps to testing team for staring testing separately without waiting for all functionalities are developed and integrated.                                                                                                                                                     
• Bugs preventing - Once tester find a bug tester can write a test and prevent that bugs re appearing in the future.that means unit testing helps developer to make refactoring and regression easier.                                                                                                                                  
• Can be used as the documentation for code - This is really important for big projects.When a new developer starts working on new project, unit testing will help developer to get better understand about existing code.                                                                                                                 
• Unit testing helps to  eliminate uncertainty in the units themselves.