MY WORDS FOR DIFFERENCE BETWEEN BLACK, WHITE AND GRAY BOX TESTING

Black Box Testing (MANUAL TESTING)

The Code Access not required. Clearly separates user's perspective from the developer's perspective through visibly defined roles. The technique of testing without having any knowledge of the interior workings of the application is Black Box testing. Large numbers of moderately skilled testers can test the application with no knowledge of implementation, programming language or operating systems.Limited Coverage since only a selected number of test scenarios are actually performed. The tester is oblivious to the system architecture and does not have access to the source code. Blind Coverage, since the tester cannot target specific code segments or error prone areas. Typically, when performing a black box test, a tester will interact with the system's user interface by providing inputs and examining outputs without knowing how and where the inputs are worked upon.Well suited and efficient for large code segments.The test cases are difficult to design. Inefficient testing, due to the fact that the tester only has limited knowledge about an application. 

White Box Testing (AUTOMATION TESTING)

It helps in optimizing the code and database. White box testing  techniques is the detailed investigation of internal logic and structure of the code. White box testing is also called glass testing or open box testing. White Box (or glass box) testing is the process of giving i/p to the system and checking how the system processes i/p to generate o/p. The tester needs to have a look inside the source code and find out which unit/chunk of the code is behaving inappropriately. Extra lines of code can be removed which can bring in hidden defects. Due to the tester's knowledge about the code, maximum coverage is attained during test scenario writing.Sometimes it is impossible to look into every nook and corner to find out hidden errors that may create problems as many paths will go untested. It is difficult to maintain white box testing as the use of specialized tools like code analyzers and debugging tools are required. Due to the fact that a skilled tester is needed to perform white box testing, the costs are increased. In order to perform white box testing on an application, the tester needs to possess knowledge of the internal working of the code.As the tester has knowledge of the source code, it becomes very easy to find out which type of data can help in testing the application effectively. 

Grey Box Testing (COMBINATION)

Grey box testers don't rely on the source code; instead they rely on interface definition and functional specifications. Grey Box testing is a technique to test the application with limited knowledge of the internal workings of an application. In software testing, the term the more you know the better carries a lot of weight when testing an application. Gray Box testing is a combination of White Box and Glass Box Testing. Testing every possible input stream is unrealistic because it would take an unreasonable amount of time; therefore, many program paths will go untested. In this, the tester has little knowledge about the internal working of the s/w; so he tests the o/p as well as process carried out to generate the o/p. There is one more type of testing called gray box testing. In this we look into the “box” being tested just long enough to understand how it has been implemented. Then we close up the box and use our knowledge to choose more effective black box tests. The test is done from the point of view of the user and not the designer.Since the access to source code is not available, the ability to go over the code and test coverage is limited. 

Mastering the domain of a system always gives the tester an edge over someone with limited domain knowledge. Based on the limited information available, a grey box tester can design excellent test scenarios especially around communication protocols and data type handling. Unlike black box testing, where the tester only tests the application's user interface, in grey box testing, the tester has access to design documents and the database. Having this knowledge, the tester is able to better prepare test data and test scenarios when making the test plan.Offers combined benefits of black box and white box testing wherever possible. The tests can be redundant if the software designer has already run a test case.