Grey Box Testing Guide | What You Should Know

Grey Box Testing

In this article in Software Testing Tutorial, we will learn What is Grey Box Testing, Grey Box Testing Techniques, its benefits, and the following. 

What is Grey Box Testing with example?

Gray Box testing is a combination of the black box and white box testing, in this technique the tester only needs limited knowledge about the internal workings of an application.

Gray Box Testing

The Gray box testing objective is to find the defects that are caused due to improper structure or improper usage of applications.

In Gray box testing the tester has access to the design document and the database whereas, in black-box testing, the tester only tests the application’s user interface. Gray box testing is also called translucent testing.

Gray box testing can be used to debug software and evaluate vulnerabilities. Here the tester knows the internal competency but is not aware of how it interacts. Thus the perspective of the tester would be similar to a potential attacker and user.

Why Grey Box Testing

  • Gray box testing would not suffer from deficiency like White box testing.
  • Gray box testing can test data domains, internal boundaries, and overflow.
  • Gray box testing checks the high-level design environment and interoperability conditions.
  • Gray box testing can find out defects that are not as easily considered by a black box or white box analysis, especially problems of end-to-end information flow and distributed hardware /software system configuration and compatibility.
  • Gray box testing can uncover several context-specific errors that are germane to web systems.
  • The Gray box test is independent of language and platform.
  • Gray box test will increase the testing coverage by focusing on all of the layers of any complex system through the combination of all existing white and black box techniques

Grey Box Testing Strategy

  • In grey box testing, it is not necessary to design test cases from the source code.
  • Testers can design test cases based on the knowledge of architecture, algorithm, internal states, or other high-level descriptions of the code.
  • Gray box testing can be done using all the straightforward techniques of black-box testing for function testing.
  • In grey box testing, the test case is generated based on given requirements and conditions before testing the program by the assertion method.

Steps to perform Grey box Testing

Step 1: To identify inputs from Blackbox testing and White box testing and select the appropriate test data.
Step 2: To identify expected outputs from those selected inputs.
Step 3: To identify all the major paths to traverse through during the testing period.
Step 4: To identify sub-functions that are part of the main functions to perform deep level testing
Step 5: To identify inputs for subfunctions
Step 6: To identify expected outputs for subfunctions.
Step 7: To start executing a test case for Subfunctions.
Step 8: To verify the correctness of the result

Grey-box Testing Techniques:

Matrix testing –

Matrix testing starts when developers define all the variables in their program, the status report of the project is stated. Each variable may inherent some technical risk, business risk and can be used with different frequency during its life cycle.

Pattern- Pattern testing as the name suggests analyses the historical data of previous system defects.
In grey box testing, the testers inspect the code and try to determine why such failures happen. These analyses will include specific reasons for the defect, which will require system analysis.
This can help the team in designing test cases, thus it helps in finding the failures proactively.
Gray box test case design gets influenced by the coding structure of the application.

Orthogonal Array- Orthogonal Array testing is a statistical testing technique usually executed in complex applications. Gray box testing combines the power of statistical testing and elaborate testing to provide the proper coverage. It helps in reducing the number combination to provide maximum coverage with the minimum number of test cases.


Regression testing is executed after making a functional improvement or repair to the program. The objective of regression testing is to determine if the change has regressed other aspects of the program.
The following testing strategies are used to execute regression testing in grey box testing:
Retest all
Retest Risky Use Cases
Retest By Profile
Retest Changed Segment
Retest within Firewall

Whitebox vs Grey box

White Box TestingGrey Box Testing
In White box testing, the internal structure and design of the application are fully known to the tester.In Gray box testing, the internal structure and design of the software application are partially known to the tester.
The tester should have full knowledge of the implementation.Testers having partial knowledge about the implementation is enough.
White box testing requires high programming skills.Gray box testing requires only basic programming skills to perform testing.
It can be executed by testers and developers.It can be executed by users, testers and developers.
It is also called clear box testing or transparent testing.It is also called translucent testing.
It is a very time consuming It is less time consuming comparatively
It is used for algorithm testingIt is not suited for algorithm testing

Blackbox vs Grey box

Black Box TestingGrey Box Testing
Black box testing does not require the tester to know the internal structure of the application.Gray box testing requires the tester to partially know about the internal structure of the application.
It is also called closed box testing.It is also called translucent testing
It doesn’t require the implementation of coding knowledge.It doesn’t require the tester to be an expert but a small amount of coding knowledge is required to execute the cases.
It is based upon the outputs and user interface of the application.It is based upon database and data flow between functions.
It is less time consuming comparatively.It is time-consuming but not as much as white box testing.
It can be executed through trial and error methods.It is executed based on the data domains.
It can improve the quality of certain aspects of the software.It can improve the overall quality of the software.


  • Gray box testing can uncover several defects that the developer have missed as it performs from the point of view of a user or attacker rather than a developer,
  • Gray box testing can improve the quality of the product by uncovering more significant vulnerabilities with less effort and cost.
  • Gray box testing allows the testing team to prioritize tests based on an understanding of the target system

Gray Box Testing Challenges

  • Testers may not be given access to the source code, this can result in missing certain critical vulnerabilities.
  • Developers might feel grey box testing if they have already run a similar test case.
  • It can be very time-consuming and unrealistic to check every potential input, i.e chances are there that certain program paths will not be tested.
  • It takes a lot of time to cover the input path for a large application, this can increase the project budget, even hamper the project deadline

Best Suited Applications

  • Grey box testing can be used for Web-based applications.
  • Gray box testing is most suited for functional testing
  • Gray box testing works well for integration testing
  • Gray box testing is most effective for evaluating business domain testing,
  • Gray box testing is used to perform security assessments.


  • Gray box testing is done from the perspective of both user and the developer, this improves its effectiveness.
  • Gray box testing combines the benefits of both black box testing and white box testing, this improves the overall quality of the application.
  • Gray box testing prevents disagreements between developers and testers as it is unbiased and non-intrusive.
  • Gray box testing helps testers to design better test cases, as it requires a partial understanding of the application’s logic.
  • Gray box testing establishes clear testing goals, making it easier for testers and developers
  • Gray box testing lets testers execute intelligent test scenarios Tester handles Ex: data type handling, communication protocol, exception handling.


  • Grey box testing can be time-consuming as it tests every single input path and sometimes it’s not realistic to do exhaustive testing.
  • The grey box can result in low test coverage when compared with white and black box testing.
  • Grey box testing is not suitable for testing some types of functionality.
  • When grey box testing is performed in distributed systems, it can be very difficult to associate defects.
  • When there is limited access to internal structure it leads to limited access code path traversal.
  • Incase of algorithm testing, grey box testing is not suited for it.
  • Designing test cases for grey box testing can be very difficult.

What are the commonly used tools for grey box testing?


Gray box testing can reduce the overall cost of the project by reducing the system defects and preventing more defects that might pass the testing stage. Gray box testing is preferred due to its moderate granularity. Gray box testing can be a very powerful technique for ensuring the software application meets the need of the intended user, performs well, and is secure. It can offer an effective approach to test the software application externally while monitoring the internal working structure

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