White-box testing (also known as clear box testing, glass box testing, transparent box testing, and structural testing) looks inside the software that is being tested and uses that knowledge as part of the testing process. If, for example, an exception should be thrown under certain conditions, a test might want to reproduce those conditions. White-box testing requires internal knowledge of the system and programming skills. It provides an internal perspective on the software under test.

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

• It is efficient in finding errors and problems
• Required knowledge of internals of the software under test is beneficial for thorough testing
• It allows finding hidden errors

• It encourages programmer's introspection
• It helps in optimizing the code
• Due to the required internal knowledge of the software, maximum coverage is obtained

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

• It might not find unimplemented or missing features
• It requires high-level knowledge of internals of the software under test
• It requires code access
• Tests are often tightly coupled to the implementation details of the production code, causing unwanted test failures when the code is refactored

White-box testing is almost always automated and, in most cases, take the form of unit tests.