Black Box vs. White Box vs. Grey Box

 

Criteria	Black Box Testing	White Box Testing	Grey Box Testing
Knowledge	No knowledge of internal code or logic.	Full knowledge of internal code and logic.	Partial knowledge of internal code and logic.
Focus	Tests functionality, inputs, and outputs.	Tests internal structures, code paths, and algorithms.	Combines aspects of both functional and structural testing.
Perspective	External perspective, as a user would interact with the software.	Internal perspective, understanding how the software works internally.	Combined perspective, balancing external and internal aspects.
Testing Level	Typically associated with higher-level testing (e.g., system testing, acceptance testing).	Associated with lower-level testing (e.g., unit testing, integration testing).	Can be applied at various testing levels, depending on the testing objectives.
Test Case Design	Test cases are derived from specifications and requirements.	Test cases are derived from code and internal system architecture.	Test cases are designed based on both external specifications and internal system knowledge.
Test Objectives	Focuses on validating functional requirements, ensuring the software meets user expectations.	Focuses on validating internal structures, ensuring code correctness and efficiency.	Aims to identify issues related to both functionality and internal code implementation.
Dependency on Source Code	No access to the source code is required.	Full access to the source code is required.	Access to partial or limited source code may be sufficient.
Testing Independence	Testers can be independent of developers.	Collaboration with developers is often necessary.	Collaboration with developers can be beneficial but is not always mandatory.
Common Techniques	Equivalence partitioning, boundary value analysis, and scenario-based testing.	Code coverage, path testing, and branch testing.	Combination of black box and white box testing techniques.
Bug Detection	Relies on identifying discrepancies between expected and actual behavior.	Detects logical errors, coding mistakes, and security vulnerabilities.	Aims to find both functional and structural defects.
Testing Visibility	Testers focus on what the system does, not on how it achieves it.	Testers have insight into the internal workings of the system.	Testers have a balanced view of both external and internal aspects.
Examples	User acceptance testing, system testing.	Unit testing, integration testing.	Database testing, API testing.