What is gray box testing?

Gray-box testing is a software testing method that combines elements of both black-box and white-box testing. The tester has partial knowledge of the internal structure or logic of the application but does not have full access to the source code.

This allows for the creation of more effective tests focused on internal mechanisms while remaining independent of complete code understanding. For example, a tester might know the database structure or API, which helps identify errors that are difficult to detect with pure black-box testing.

For instance, when testing a web application, the tester knows which requests are sent to the server and what data is expected but does not have access to the server-side source code.