Comparison of White Box Testing , Black Box Testing and Grey Box Testing:

1) White Box Testing Technique:

                   It is the detailed investigation of internal logic and structure of the code. In white box testing it is necessary for a tester to have full knowledge of source code.

2) Black Box Testing Technique: 

                  It is a technique of testing without having any knowledge of the internal working of the application. It only examines the fundamental aspects of the system and has no or little relevance with the internal logical structure of the system.

3) Grey Box Testing Technique:

                 White box + Black box = Grey box , it is a technique to test the application with limited knowledge of the internal working of an application and also has the knowledge of fundamental aspects of the system. 

Black Box Testing	Grey Box Testing	White Box Testing
Analyses fundamental aspects only i.e. no proved edge of internal working	Partial knowledge of internal working	Full knowledge of internal working
Granularity is low	Granularity is medium	Granularity is high
Performed by end users and also by tester and developers (user acceptance testing)	Performed by end users and also by tester and developers (user acceptance testing)	It is performed by developers and testers
Testing is based on external exceptions – internal behavior of the program is ignored	Test design is based on high level database diagrams, data flow diagrams, internal states, knowledge of algorithm and architecture	Internal are fully known
It is least exhaustive and time consuming	It is somewhere in between	Potentially most exhaustive and time consuming
It can test only by trial and error method	Data domains and internal boundaries can be tested and over flow.	Test better: data domains and internal boundaries