Grey box testing


Grey box testing is the testing technique which combines black box and white box testing methodologies. It aims to uncover internal structure as well as external functional defects. The tester has an understanding of the product’s functional behavior and also has partial knowledge about the internal architecture of the product. It integrates the knowledge of internal data structures and algorithms of the product together with testing at the user interface level.  Therefore, this testing offers the advantages of both black box and white box testing.

Grey box testing example

Grey box testing is primarily useful while testing web applications. An example of grey box testing can be when tester tries to test password change functionality from the login page. He inputs the new details from the front end and verifies the changes in credential details in the backend or database and then checks the system behavior for those updated credentials.

Therefore, here tester aims at both verifying the front end functionality plus checking if the changes are reflected in the database. Also, he can evaluate the internal algorithms responsible for these changes.

Why Grey box testing

Grey box testing is a hybrid testing approach offering advantages from both black box and white box testing techniques. Hence it is quite suitable in modern times for the projects where they don’t have a timeline to implement both black box and white box testings. This testing focuses on functional requirements and specifications plus architectural design documents, UML diagrams and data flows. Despite involving evaluation of the architectural view of the product, it does not verify the source code. Hence, it maintains the status of unbiased testing from the development perspective.


  • Grey box testing packs the benefits of performing black box and white box testing in one testing.
  • It is quite effective as it covers all aspects of the product whether functional or design.
  • Grey box testing tests the system from users plus developers point of view.
  • It offers the best way to test intelligent test scenarios in and out.


  • It is a short cut way to performing both black box and white box testings resulting in lower code coverage.
  • Grey box testing is a time-consuming testing process as needs to test the item internally and externally both.
  • Complex white box testing scenarios cannot be covered in grey box testing due to the lack of required knowledge and technical skills.


To conclude, grey box testing is definitely an intelligent way of combining traditional black box and white box testing techniques offering the benefits of both the worlds. Not only does it verifies the system from the user’s interface of view but also its internal well being. At the same time, it can not completely replace them due to the challenges it faces.

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