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Black box, White box, and Grey box testing: Major distinctions QA / Software Testing

Jul 13, 2020 Namiko

Black box, White box, and Grey box testing: Major distinctions

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Software systems are now ingrained in the fabric of our daily lives, from business apps to consumer products. Unfortunately, even a single experience with faulty software may result not only in heavy financial losses for businesses, such as reputation damage and customers, but also potentially lead to life-threatening incidents if used by medical or mission-critical applications. To mitigate these risks, software quality testing is becoming increasingly necessary across many industries reliant on digital incomes; ensuring quality while reducing potential failure rates when it comes time for launch day operations.

One of the common misconceptions of testing is that people think it only consists of running tests, i.e., executing the software and checking the results in an excel sheet. On the contrary, software testing actually is a process that involves complex activities such as checking the test base itself off errors and test execution. The testing activities also stretch to things like test planning, analyzing, designing, and implementing tests, reporting, and evaluating the quality of a test object.

Some testing does involve the execution of the component or system being tested; such testing is called dynamic testing. Other testing does not involve the execution of the component or system being tested; such testing is called static testing. Also, testing includes reviewing work products such as requirements, user stories, and source code. Despite another common misconception about testing that focuses entirely on verification, it performs both verification and validation. For example, verification of requirements, user stories, or other specifications and validation checking whether the system will meet user and other stakeholder needs in its operational environment.

Now that we have a baseline understanding of the testing concepts, this article compares different types of testing — Black, White, and Grey boxes.


BLACK BOX TESTING is defined as a testing technique in which functionality of the “Application Under Test” is tested without looking at the internal code structure, implementation details, and knowledge of the internal paths of the software.

In other words, with black box testing, we solely focus on the inputs and outputs of the software system without bothering about internal knowledge of the software program. So, in the above black box, an object can be any software system you want to test. For Example, an operating system like Windows, a website like Google, a database like Oracle, or even your own custom application.

This technique is useful when it comes to unit, integration, system, and acceptance testing.


WHITE BOX TESTING is a method of software testing that tests the internal structures or workings of an application, as opposed to its functionality like black box testing. It is also known as clear box testing, glass box testing, transparent box testing, and structural testing. In white box testing, an internal perspective of the system as well as programming skills are put to test and used to design test cases.

When developing a new digital product, it is almost mandatory to incorporate white box tests in your regular quality assurance routine. Basically, the tester chooses inputs to exercise paths through the code and determines the expected outputs. Therefore, white-box testing can be applied at the unit, integration, and system levels of the software testing process.

Although traditional testers tended to think it is best being done at the unit level, it is used for integration and system testing more frequently today. It is because it can test paths within a unit, paths between units during integration, and between subsystems during system-level tests.

In order to avoid having errors appear in syntax or spelling, loop structures, code paths, and implementation of code elements into a program, white-box testing is recommended with the following code coverage criteria:

  • Control flow testing
  • Data flow testing
  • Branch testing
  • Statement coverage
  • Decision coverage
  • Modified condition/decision coverage
  • Prime path testing
  • Path testing


GREY BOX TESTING is a combination of white-box testing and black-box testing. The aim is to search for defects if any due to improper structure or improper usage of applications.

As we know, in white-box testing, understanding the internal structure of the system is essential, but in black-box testing, this knowledge is not so necessary. How about in-grey box testing? Under grey-box testing, testers should have a partial understanding of the structure of the system relevant to the test as well as access to the database. Grey box testing is often used in integrated testing. However, based on algorithms and functions, it can also be used at various test levels.

I would like to note that grey box testing comes with a set of advantages because of various reasons, especially because of the increasing need for speedy and effective testing to satisfy current-day consumers that can be demanding. A lot of modern-day web-based applications require effective testing because of a high level of expectations for performance, as well as the amount of numerous data and functions being added on daily basis.

It is important to perform both grey box and black box testing in many cases for applications. And if there are a huge amount of errors found, a combination of grey box and black box testing helps in identifying problems and boosting performance.


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