Gray Box Testing
Gray box testing combines elements of both black box and white box testing — the tester has partial knowledge of the internal code or architecture (database schema, API contracts, system design) but tests primarily from the outside, the way a user or client would. It's the pragmatic middle ground most real-world testers actually work in.
A pure black box tester has zero visibility into the code; a pure white box tester is essentially reading and testing the implementation directly. Gray box testing sits between: knowing the database schema helps a tester design more targeted test data, and knowing the API contract helps design more precise request/response assertions, without requiring the tester to read or write the underlying implementation.
Most API testing and integration testing in practice is gray box by nature — testers work from documented contracts and architecture diagrams, which is more information than a strict black box approach assumes, without going as deep as full code-level white box testing.
