Black box testing, white box testing, and grey box testing are three different software testing techniques used to evaluate the functionality and reliability of a software application.
Black Box Testing:
In black box testing, the tester does not have any knowledge of the internal workings of the application being tested. The tester focuses only on the inputs and outputs of the system, and evaluates its behavior without any understanding of the code or the implementation details. Black box testing is primarily focused on the functional requirements of the application and helps in identifying defects that could impact the usability or performance of the application.
- Black box testing is usually performed by Software test engineer (Quality Analyst)
- Programming Knowledge is not required for performing black box testing.
- It is also known as Close Box Testing, Opaque Box Testing and Functional Testing.
- Examples of Black box testing are Retesting, Regression Testing, System Testing etc.

Black box testing can be performed manually or through automated testing tools. It is an effective way to ensure that the software meets the user’s requirements and specifications, and can help identify defects and issues that may not have been apparent during development.
White Box Testing:
White box testing, on the other hand, is a testing technique in which the tester has full access to the source code of the application being tested. The tester can analyze the code and evaluate the internal workings of the system, with the aim of identifying any potential defects or vulnerabilities that could impact the performance or security of the application. White box testing is typically used for testing applications that are mission-critical or require high levels of security.
- White box testing usually performed by Software Development Engineer (SDE)
- Programming knowledge is must for White Box Testing.
- It is also known as Clear box, Glass box, Open Box, Transparent, Structural testing
- Examples of White box Testing are Unit Testing and Mutation testing.

In white box testing, the tester analyzes the internal working of the software to ensure that it functions as expected and meets the specified requirements. This type of testing is often used to verify the correctness of the software code and to check the flow of control within the software. The tester may also use techniques such as code coverage analysis to ensure that all parts of the code are executed during testing.
Some common white box testing techniques include:
- Statement Coverage: In this technique, the tester ensures that each statement in the code is executed at least once during testing.
- Branch Coverage: This technique is used to ensure that all possible branches in the code are executed during testing.
- Condition Coverage: In this technique, the tester ensures that all possible combinations of conditions in the code are tested.
- Path Coverage: This technique involves testing all possible paths through the software code.
Grey Box Testing:
Grey box testing is a combination of both black box and white box testing. In grey box testing, the tester has limited access to the source code of the application being tested. The tester has some knowledge of the internal workings of the system but not enough to fully understand its implementation details. Grey box testing is typically used to evaluate the functionality and usability of the application while also identifying any potential defects or vulnerabilities that could impact its performance or security.
Some common techniques used in grey box testing include boundary value analysis, equivalence partitioning, and error guessing. Grey box testing can also involve running manual or automated tests, analyzing logs and system outputs, and using debugging tools to gain insights into the system’s behavior.

Overall, grey box testing can be a powerful tool for ensuring the quality and reliability of software systems, particularly in complex environments where full knowledge of the system’s internals is not possible.
All three testing techniques are essential for ensuring the quality and reliability of software applications, and their selection is based on the specific requirements and goals of the testing process.
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