What is Black box testing and what are its advantages and disadvantages ?

Black box testing is a test design method. It treats the system as a "black-box" so it does not explicitly use the knowledge of the internal structure. In other words, the test engineer does not require to know the internal working of the black box. Black box testing focuses on the functionality part of the module. Black box testing is also known as opaque box and closed box testing. While the term black box testing is more commonly, many people prefer the terms "behavioral" and "structural" for black-box and white-box respectively.
There are bugs that cannot be found using only black box testing or only white box testing. If the test cases are extensive and the test inputs are also from a large sample space then it is always possible to find majority of the bugs through black box testing.

The basic functional or regression testing tools capture the results of black box tests in a script format. Once captured, these scripts can be executed against future builds of an application to verify that new functionality has not disabled previous functionality.

Advantages of Black Box Testing
- It is not important for the tester to be technical. He can be a non-technical person.
- This testing is most likely to find those bugs as the user would have found.
- Testing helps to identify the vagueness and contradiction in functional specifications.
- Test cases can be designed as soon as the functional specifications are complete.

Disadvantages of Black Box Testing
- There are chances of repetition of tests that are already done by the programmer.
- The test inputs needs to be from large sample space.
- It is difficult to identify all possible inputs in limited testing time. So, writing test cases is slow and difficult.
- There are chances of having unidentified paths during testing.