Gray Box Testing

Gray box tests are a combination of white-box and black-box testing methods. They are used to test a product or application with partial knowledge of the application's internal structure. The purpose of this testing is to search for and identify defects caused due to improper application structure or usage.

Some of the key characteristics of gray box testing are:

• It is a combination of white-box methods (with complete code knowledge) and black-box methods (with no code knowledge).
• System defects can be reduced or prevented by applying gray box testing.
• It is more suitable for GUI, functional, security, web applications, etc.

In this process, context-specific errors related to web systems are commonly identified. This improves test coverage by focusing on all layers of any complex system.

In QA, gray box testing provides an opportunity to test both the front-end and back-end of an application.

Why Apply Gray Box Testing?

Some of the benefits of applying gray box testing include:

1. It provides the combined benefits of both other modalities.
2. It combines input from developers and testers, enhancing the overall product quality.
3. It reduces the overall cost throughout the functional and non-functional testing process.
4. It provides developers enough time to fix defects.
5. Testing is done from a user's perspective rather than a designer's viewpoint.

Gray Box Testing Strategy

To perform gray box testing, the tester does not need access to the source code.

A test is designed based on knowledge of algorithms, structures, architectures, internal states, or other high-level descriptions of program behavior.

Techniques Used for Testing

The primary techniques used for gray box testing are:

• Matrix Testing: This testing technique involves defining all variables that exist in a program.
• Regression Testing: To check if the change in the previous version has regressed other aspects of the program in the new version. This will be done by testing strategies like retest everything, retest risky features, and retest within a firewall.
• Matrix or Action-Oriented Testing (OAT): Provides maximum code coverage with a minimum number of test cases.
• Pattern Testing: This technique is performed on historical data from the previous version's defects in the system. Unlike black-box testing, gray box testing operates by digging into the code and determining why the failure occurred.

Steps to Apply Gray Box Testing

Let's look at the steps to apply gray box testing:

1. Identify the inputs.
2. Identify the outputs.
3. Identify the main paths.
4. Identify the sub-functions.
5. Develop inputs for the sub-functions.
6. Develop outputs for the sub-functions.
7. Execute test cases for the sub-functions.
8. Verify the correct result for the sub-functions.
9. Repeat steps 4 & 8 for other sub-functions.
10. Repeat steps 7 & 8 for other sub-functions.

Note that gray box test cases may include:

• GUI-related.
• Security-related.
• Database-related.
• Browser-related.
• Operating System-related.