We provide Structural Testing which is a testing of the external behaviour of the program, also known as black box testing. It is usually a functional testing.
Structural testing is the type of testing carried out to test the structure of code. It is also known as White Box testing or Glass Box testing. This type of testing requires knowledge of the code, so, it is mostly done by the developers. It is more concerned with how system does it rather than the functionality of the system. It provides more coverage to the testing.