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Home Guide What is Grey Box Testing? (Techniques & Example)

What is Grey Box Testing? (Techniques & Example)

By Tom Collins, Community Contributor -

Starting your testing in the SLDC is essential to find more bugs and fix them before they reach the later stages. By taking this strategy, your organization gains more productivity and profit.

You can choose from different software testing types: black box testing, white box testing, and grey box testing. This article will emphasize the grey box technique and understand it in length.

What is GreyBox Testing?

In black box testing, you don’t have access to the internal coding, and there is no need to understand the coding. But in white box testing, you must work with the internal coding, structure, and algorithm.

  • Grey box testing is where these two merges and the tester has partial knowledge of the internal details of your systems and the outer details as per the requirements.
  • The testing becomes helpful in system integration testing, web application testing, security, and business domain testing.

Purpose and Significance of Grey Box Testing

  1. The purpose of this testing specifies to improve the products’ quality by using both functional and non-functional testing. Thus, it saves time from the lengthy and complex process of testing. 
  2. This testing enables penetration testing for your system. It checks the security of the system by ensuring that unauthorized users and attackers can’t access your system. So, it checks if your application’s functionality goes as per the requirements of the authorized users.
  3. Another important point is that it requires evaluating an applicant’s internal states, architecture, and behavior. 
  4. Also, it checks an application’s external behavioral approach (non-functional). Hence, the testers gain almost complete knowledge about the app and fix the bugs efficiently.

Advantages and Limitations of Grey Box Testing

Advantages of Grey Box Testing
Improved test coverageYou have to perform this testing both through the aspect of developers and testers. Hence it will earn more test coverage and thereby improves your product quality.
Efficient use of resourcesIt’s a type of semi-transparent testing. The testers know the working process of different components for this testing. They can access several documents, database diagrams, flow charts, and more. Thus the testers can create the best test scenarios for testing.
Early detection of defectsThis testing gives the testers partial knowledge of software codes, users’ perspectives (how to operate the system), and how to protect them from potential attackers. 

Thus adopting different knowledge, the testers identify issues you can’t detect from other testing. As a result, the testers detect the bugs in the early stages and the developers get enough time to fix them.


Limitations of Grey Box Testing
Limited access to internal codeYou don’t need to understand the entire internal structure and algorithm for this testing. 

Thus, there will be limited access to the internal coding of the system, and sometimes it becomes difficult to find out the root causes of the defects.

Dependency on system knowledgeFor this kind of testing, there is no necessity to know the thorough implementation of the system. 

So, it indicates a need for more knowledge of the testers about the system. Thus testers may need help to create test cases for complex systems.

Techniques of Grey Box Testing

1. Boundary Value Analysis 

The boundary value analysis technique tests the input values on or within the boundary of a specific range for the system’s input domain. If you enter any value beyond this range, your system gives error messages or unexpected behavior. The system’s program can’t handle cases when you enter an unexpected input value, and it shows an error. 

You can further divide this technique into two categories – inner boundary testing and outer boundary testing.

  • For the inner boundary, you have to enter values within the range. So, it will give a positive outcome.
  • For the outer boundary, you need to enter values beyond the ranges. That will give a negative outcome and a result of test failure.

For example, your system takes input between 1 and 50. When you give a value of 1 or 50, or between these two numbers, your test has passed. It is inner boundary testing. On the other hand, when you enter values like 0 or 51 or other integers, your test becomes unsuccessful. So it’s outer boundary testing.

A common application of this testing is your mobile number field in any app or web. This field only allows entering the integers between 0 and 9. The system will show an error message if you enter 10 or other integers.

2. Decision Table Testing

With decision table testing, you must test your system’s behavior according to the multiple inputs. This total procedure will be captured in the form of a table. That means the table shows the inputs and their respective outputs.

A loan amortization table is a practical example of decision table testing. You must enter the inputs – year (annual)/ month (monthly), total interest, and principal amount within your online loan EMI calculator. The calculator will present these inputs and their corresponding outputs (outstanding balances) in a tabular format.

3. State Transition Testing

State transition testing checks the behavior of an application when it goes through different states and transitions. A state indicates a condition or set of conditions under which you must perform the testing. The transition indicates the change from one condition to another condition.

This testing aims to identify whether the system behaves as expected within all the possible states and transitions. So, you must prepare the test cases to verify the states and check the transitions are happening without any bottleneck.

For example, when you pay any bill through your mobile banking application, you have to test the following states

  1. Verifying your bill details and the biller’s name
  2. Initializing the payment with the ‘Proceed to pay’ button’
  3. Choosing a payment method
  4. Entering security credentials (PIN/ CVV number, etc.)
  5. Payment confirmation

So, the transition path will be

Verifying bill and the details of the biller> initializing payment > choosing payment method > entering security credentials > payment confirmation.

Grey Box Testing Example in Action

1. Description of the software system being tested

First, you must have an understanding of the system. Suppose we are testing an e-commerce website. So, you have to know the basic functionalities of that site and which features are the best for the users. Through an e-commerce site, people buy and sell products. The merchants process orders, handle shipping, and logistics, manage payments, and provide other services for the customers.

2. Selection of a specific testing scenario

Then you have to select a specific testing scenario. For example, you may need to test the ordering process through the site. So, you have to create your grey box test cases based on those scenarios.

The test scenarios include:  searching products > adding products to the cart > checking out the product details > entering payment and delivery details > verification of the details > payment completion > order completion.

3. Application of Grey Box Testing Techniques

You must apply the state transition technique to test the order processing. This technique is suitable for a product ordering method through an e-commerce application. It helps you to test all the states and transitions effortlessly.

4. Results and observations from the testing process

Finally, you get the test results through the test technique. You should observe the behavior of your system in every state and transition. If the system behaves exactly as per expectation, your test becomes successful. Otherwise, you have to identify the defects and report them to the developer for fixing them.

Closing Notes

Grey box testing is a crucial technique in any SDLC. With this technique, you can learn both black-box and white-box testing. This testing is more useful for database and security testing purposes

You need automated approaches when you perform grey box testing, as it requires some coding. You can use frameworks like Selenium, Appium, and Cypress on BrowserStack for automation testing.

  • BrowserStack Real Device Cloud offers 3000+ real devices and browsers to test your apps and web. 
  • Test real user conditions like network simulation, geolocation testing, and more. 
  •  Again, you can try out local testing features to test your apps on the development and launching environments. You don’t need any extra setup for this.
  • Additionally, there are CI/CD tools like JIRA, Jenkins, bamboo, etc. BrowserStack provides integrations of all these automation frameworks and CI/CD tools.

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1. What is Greybox vs Whitebox?

The grey box technique is the blend of white box and black box testing. That means you need to test some coding and non-coding elements. But in white box testing, you require only to test coding.

2. For which purpose Grey box testing is best suitable?

The grey box is best suitable for the Database and the security testing. In these cases, you need knowledge of black-and-white box testing.

3. Which perspective is required for the grey box testing?

Almost, it is done from the users’ perspective. But the tester needs a minimum of coding knowledge to perform this test. The ultimate goal of this testing is to improve the quality of a product.

4. Is grey box testing automated or manual?

You can perform it by both manual and automated approaches. You have to choose the approach based on the testing requirement.

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