Grey Box Testing

Example of Grey Box Testing:
Imagine a tester is validating a user registration feature. They do not have access to the code but know that when a user signs up, the data should be stored in a particular database table. So they not only check the form on the screen but also verify whether the correct data is saved in the database after submission. This extra layer of understanding helps in catching deeper issues like incorrect data mapping or missing validations at the backend. 

Grey box testing is often used in integration testing or when working with APIs, databases or workflows that involve both user actions and backend logic.

Grey box testing is a combination of black box and white box testing which involves partial knowledge of coding structure. Grey box testing is best suited for integration testing, security testing, session management, API testing etc. Unlike Black box testing which focuses on top layer or white box testing which focuses on coding layer, here we mainly focus on all layers of the software or in other terms business logic is considered for Grey box testing.

Few examples:

API Testing

If we want to test Role based software like access for Admin user and Normal user. Apart from doing black box testing, We need to know the APIs being called for each kind of user. Authorising a Normal user and trying to hit the API for an admin user should result in 401 (Unauthorised) or 403(Forbidden). 

Session Management:

For every login we have a session maintained for a particular duration. As part of black box we do logout and check if the user is logged out. 

As part of Grey box testing, if we know where the session details are stored at client or server end then we can play around with those ensuring that it works properly