Black-box testing (also known as functional testing) treats software under test as a black box without knowing its internals. Tests use software interfaces and try to ensure that they work as expected. As long as the functionality of interfaces remains unchanged, tests should pass even if internals are changed. The tester is aware of what the program should do, but does not have the knowledge of how it does it. Black-box testing is the most commonly used type of testing in traditional organizations that have testers as a separate department, especially when they are not proficient in coding and have difficulties understanding it. This technique provides an external perspective on the software under test.

Some of the advantages of black-box testing are as follows:

• It is efficient for large segments of code
• Code access, understanding the code, and ability to code are not required
• It offers separation between users and developers perspectives

Some of the disadvantages of black-box testing are as follows:

• It provides limited coverage, since only a fraction of test scenarios is performed
• It can result in inefficient testing due to tester's lack of knowledge about software internals
• It can lead to blind coverage, since testers have limited knowledge about the application

If tests are driving the development, they are often done in the form of acceptance criteria that is later used as a definition of what should be developed.