Through white box penetration testing, you can test every single existing condition and even the ones that are not possible with black box testing. The pen tester’s reach increases with complete knowledge of the system and the network infrastructure. The process exposes more vulnerabilities along with inconspicuous bottlenecks that may go ignored during black box tests. (EC Council)

In security, we refer to testing done on the inside, maybe even having access to the source code, as white box testing–the application and network information is available to the tester. You can also bring someone in from the outside and give them some, but not alot of information, that’s grey box testing. And there’s black box testing, where the third party has no knowledge of the applications or network. (Security Boulevard)

Black Box testing is a type of Dynamic Testing, it is defined as a testing technique in which functionality of the Application Under Test (AUT) is tested without looking at the internal code structure, implementation details and knowledge of internal paths of the software. (HackerNoon)