Testing plays a vital role in development of stable and secure software solutions and verify that software performs as expected. Most common approaches of software testing are white box testing, black box testing and gray box testing. White box testing and black box testing have their own pros and cons. Gray box testing combines two testing approaches so as to overcome their deficits. It aims to amend the loopholes and shortcomings found in white box and black box testing. It has been developed to be a beneficial blend of the two testing techniques. In Grey box testing, testers have access to the design document and database rather than only the user interface. It is also called translucent testing. This kind of testing can be used to debug software and evaluate vulnerabilities. Before digging to the details of Grey box testing, let us see what is Grey box testing?

What Is Grey Box Testing?

Grey box testing is a testing technique which is a combination of White box testing and black box testing. In white box testing the internal structure of product is known whereas in black box testing internal structure is unknown to the tester. In Grey box testing internal structure is partially known and it includes access to internal data structures and algorithms to design the test cases. Commonly it focuses on context-specific errors related to web systems. Grey box testing is a great way to find security flaws in programs. It can help to discover bugs or exploits because of the incorrect code structure or incorrect use of applications.

Grey box tester takes the code-specific approach of white box testing and combines it with various approaches of black box testing such as functional testing and regression testing.

Need Of Grey Box Testing-
Grey box testing is independent of platform and language
It can test data domains, internal boundaries and overflow.
Checks the high level design environment and interoperability conditions
It can detect defects that are not easily detected by black box or white box analysis, like end to end information flow, distributed hardware/software system configuration and compatibility.
This testing can uncover several context-specific errors
It combines the input of developers as well as testers and improves overall product quality

How To Perform Grey Box Testing?
While performing gray box testing, it is not necessary to design test cases from the source code. Testers can design test cases as per algorithms, internal states or high-level description of code. Let us see the steps to perform grey box testing.

Steps To Perform Grey Box Testing-

1. Identify inputs from Blackbox testing and white box testing and select the appropriate test data.
2. Identify the expected outputs from the selected inputs Recognize the major paths to traverse through during the testing period
3. Identify the sub-functions that are part of main functions to do deep level testing
4. Point out inputs for subfunctions
5. Identify the expected outputs for subfunctions
6. Start execution of test case for subfunctions
7. Verify correctness of result

Grey Box Testing Techniques-

1. Matrix Testing-
It begins when developers define variables in their program, status report of the project is stated. Every variable may inherent technical risks, business risk and also can be used with different frequency during its life cycle.

2. Pattern Testing-
It analyses the historical data of previous system defects. Testers inspect the code and try to determine the reason for failure. This can help the team in test case designing and so helps in finding the failures proactively. This kind of test case design gets influenced by coding structure of app.

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

4. Regression-
To check whether the change in the previous version has regressed other aspects of the program in the new version. It will be done by testing strategies such as retest all, retest risky use cases, retest within a firewall.

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