Comparison of Black Box and White Box Testing:

While White Box Testing (Unit Testing) validates internal structure and working of your software code,the main focus of black box testing is on the validation of your functional requirements.

To conduct White Box Testing , knowledge of underlying programming language is essential. Current daysoftware systems use a variety of programming languages and technologies and its not possible to know all of them. Black box testing gives abstraction from code and focuses testing effort on the software system behaviour.

Also software systems are not developed in a single chunk but development is  broken down  in different modules. Black box testing facilitates testing communication amongst modules (Integration Testing) .

In case you push code fixes in your live software system , a complete system check (black box regression tests) becomes essential.

Though White box testing has its own merits and help detect many internal errors which may degrade system performance

Black Box Testing and Software Development Life Cycle (SDLC)

Black box testing has its own life cycle called Software Test Life Cycle (STLC) and it is relative to every stage of Software Development Life Cycle.

• Requirement - This is the initial stage of SDLC and in this stage requirement is gathered. Software testers also take part in this stage.
• Test Planning  & Analysis - Testing Types applicable to the project are determined. A Test Plan is created which determines possible project risks and their mitigation.
• Design - In this stage Test cases/scripts  are created on the basis of software requirement documents
• Test Execution- In this stage Test Cases prepared are executed. Bugs if any are fixed and re-tested.