Grey Box Testing: An Interesting Guide For 2021


Every business expects that its new products and new applications are full proof, free from defects, and gives the desired results that they are meant for. And for that purpose, each and every application needs to undergo software testing. It detects failures so that defects may be identified beforehand and corrected before the appearance in the critical environment. Testing not only prevents losses due to bugs or issues but also helps in giving a productive application too, thus software testing acts as a savior to the businesses. The software techniques like Grey Box Testing do exactly the same and help in achieving the desired software that is reliable, responsive, flawless, and easy to use.

However, the most popular techniques in this field are Black-Box, White-Box, and Grey-Box testing methods, which effectively assist developers in making their code bug-free and keeping functionality in check. While all three work on different aspects, Gray Box Testing is more advantageous amongst these. It is a combination of both Black-Box Testing and White-Box Testing methods and neutralizes most of their flaws. Now, let’s discuss in details what is Grey Box Testing.

  1. What is GB Testing?
  2. Grey Box Testing Strategy
  3. Grey Box Testing Challenges
  4. Advantages of Grey Box Testing
  5. Grey Box Testing Example

1. What is GB Testing?

Grey Box Testing is a software testing technique that tests for any defects or malfunctions with only partial knowledge of the applications. It is actually the blend of White Box Testing and Black Box Testing and looks for the incorrect structure or inappropriate usage of applications. The process of Gray Box Testing identifies the context-specific errors related to web systems and concentrates on each layer of any of the complex system.

Before moving further, we need to understand what is Grey Box, and what does Grey Box Testing means? The Grey Box method focuses on all the layers of the software and tests them regardless of the complexity. It targets the system using a straightforward Black-Box strategy that makes testing an easy task. Anyone from developers to testers to end-users can do the job and make the applications error-free. 

While Black-Box testers test interfaces and functionality, the White-Box testers check the internal structure to correct the source code of the software; both these approaches have their share of pros and cons. To conquer the deficiencies and uncertainties involved with these types of testing, a new approach was developed as a productive amalgamation of the White Box and Black Box Testing. It tests interfaces, functionality, and internal structures in a non-intrusive manner. 

Gray Box Testing is given this name as the software program is like a semi-transparent or Gray Box, which the tester can partially observe. It detects context-specific errors linked to web systems and was developed keeping in mind the following objectives: 

  1. To make use of the maximum benefits of both Black Box Testing and White Box Testing.
  2. To deliver the best results based on the combined input of developers and testers.
  3. To promote overall product quality by reducing the overhead of the lengthy procedure of functional and non-functional testings.
  4. To give enough time to developers to fix defects and develop the products keeping in mind the user’s point of view.

Gray Box Testing definition can be simply put as the productive sum of White Box Testing and Black Box Testing as shown in the following Grey Box Model:

Black Box Testing   White Box   Testing = Grey Box Testing


The upper diagram clearly explains what is Gray Box Testing, while its methodology as mentioned below explains in detail the technique involved:

  • This method involves the analysis and understanding of the internal features of the application using White Box Testing and then designing tests based on these understandings.
  • Later, these developed test cases are executed using Black Box Testing techniques that check the qualities of the software application.

This methodology works best as the integration testing and penetration testing and is best suited for checking web applications and business domains. In the Grey Box Penetration Testing, a tester works on partial knowledge about the system and reduces threats and risks. This type of Gray Box Penetration Testing is also known as the GreyBox Pentest.

2. Grey Box Testing Strategy

To carry out the Grey Box Testing process, test cases are designed after observing the algorithm, architectures, internal states, other program behavior, or the source code. The steps performed for achieving this are as follows: 

  • Step 1: Identification of White Box Testing inputs and Black Box Testing inputs.
  • Step 2: Identification of probable outputs.
  • Step 3: Identification of all significant paths that may pass through during the testing phase.
  • Step 4: Identification of sub-functions to perform deep level testing.
  • Step 5: Developing inputs for sub-functions.
  • Step 6: Developing outputs for sub-functions.
  • Step 7: Execution of a test case for sub-functions.
  • Step 8: Verification of the results of the test.
  • Step 9: Repetition of Steps 4 and 8 for other Subfunctions.
  • Step 10: Repetition of Steps 7 and 8 for other Subfunctions.

The Grey Box Testing includes the test cases that are either Security-related, Database related, Browser related, GUI related, or Operational system related. Usually, this methodology utilizes automated software Grey Box Testing tools to check the threats and saves the tester from manual checking. Several Gray Box Testing techniques are used as per the requirements of the applications, including: 

  • Matrix Testing: This is one of the most significant Grey Box Testing techniques in which risks are examined by defining all the variables that exist in the programs.
  • Regression Testing: This testing is done after every change in the software to check whether new functionalities are affecting the existing functioning of the system.
  • Orthogonal Array Testing or OAT: It is used for complex applications and provides maximum code coverage with minimum test cases using n numbers of permutations and combinations.
  • Pattern Testing: This testing is performed on the previous system defects, which helps test cases in finding other threats well before hitting production.

3. Grey Box Testing Challenges 

  • It is difficult for distributed systems and not suitable for algorithm testing. 
  • Due to limited access to the internal structure, the access for code path traversal is also limited.
  • It fails if any component under the test crashes or when the content of the outcome is inaccurate.

4. Advantages of Grey Box Testing

  • Users and developers have clear mindsets.
  • Tests are performed from the user’s perspective.
  • Non-intrusive.
  • Does not require highly skilled programmers.
  • Improves the overall quality of the product using the benefits of both Black Box and White Box Testing.
  • Gives more time to developers for defect fixing.
  • Very efficient as integration testing.

5. Grey Box Testing Example

Now, let’s understand what is Grey Box Testing with example, if the website under testing encounters any problem while clicking on any link, its HTML code is changed to get the desired results and that undergoes further checking. Here, code alteration is White Box Testing while front end testing is Black Box Testing.


Grey Box Testing is a robust tool for securing software from diverse threats and defects by investing less effort and cost. It reduces the overall expense by detecting defects at an earlier stage and preventing these from passing further, and in-turn delivering a productive application.

So, have you made up your mind to make a career in Cyber Security? Visit our Master Certificate in Cyber Security (Red Team) for further help. It is the first program in offensive technologies in India and allows learners to practice in a real-time simulated ecosystem, that will give you an edge in this competitive world.


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