White Box Testing

White Box Testing

A software testing technique is also known as glass boxstructuralclear box and open box testing, white box testing whereby explicit knowledge of the internal workings of the item being tested is used to select the test data.

Unlike black box testing, white box testing uses specific knowledge of programming code to examine outputs. The test is accurate only if the tester knows what the program is supposed to do. He or she can then see if the program diverges from its intended goal. White box testing does not account for errors caused by omission, and all visible code must also be readable.

Gaining a deep understanding of the system or component is possible when the tester understands these at program- or code-level. So almost all the time, the tester needs to either understand or have access to the source code that makes up the system – usually in the form of specification documents.

Armed with the level of technical detail that is normally visible only to a developer, a Tester will then be able to design and execute test cases that cover all possible scenarios and conditions that the system component is designed to handle.

The key principles that assist you in executing white box tests successfully are:

  • Statement Coverage– ensure every single line of code is tested.
  • Branch Coverage– ensure every branch (e.g. true or false) is tested.
  • Path Coverage– ensure all possible paths are tested.

And we know path coverage is favored above branch coverage for the sheer comprehensiveness it provides.

When is White Box Testing appropriate?

You know by now, that such intensive testing is not for everyone or every situation.

The rigour that white box Testing employs is quite useful – yes, but not all the time.

white box Testing is usually reserved for mission-critical systems and components, because, well, such systems simply deserve the attention to detail that this technique can bring.

Mission Critical

By mission critical, we mean any system that provides such critical utility to a company; organization or government needs to be bug-free. Any level of bugs or downtime is unacceptable for such systems, as they perform extremely vital functions for the stakeholders involved.

It could quite literally mean a difference between life and death if such systems do not work as expected:

  • Customers could be cut off from accessing their money when in life-changing situations – say when they’re trying to pay for a loved one’s emergency treatment at a hospital.
  • An entire country’s security could be compromised by a malfunctioning IT system.

So where critical systems and components are involved, it is necessary to ensure they are bug-free And making a mission-critical system bug-free, in turn, depends on employing extensive testing.

 Levels Applicable To

White Box Testing method is applicable to the following levels of software testing:

  • Unit Testing: For testing paths within a unit.
  • Integration Testing: For testing paths between units.
  • System Testing: For testing paths between subsystems.

However, it is mainly applied to Unit Testing so I will explain on unit testing only.

UNIT TESTING is a level of software testing where individual units/ components of a software are tested. The purpose is to validate that each unit of the software performs as designed. A unit is the smallest testable part of any software. It usually has one or a few inputs and usually a single output. In procedural programming, a unit may be an individual program, function, procedure, etc. In object-oriented programming, the smallest unit is a method, which may belong to a base/ super class, abstract class or derived/ child class. (Some treat a module of an application as a unit.


  • Testing can be commenced at an earlier stage. One need not wait for the GUI to be available.
  • Testing is more thorough, with the possibility of covering most paths.


  • Since tests can be very complex, highly skilled resources are required, with a thorough knowledge of programming and implementation.
  • Test script maintenance can be a burden if the implementation changes too frequently.
  • Since this method of testing is closely tied to the application being tested, tools to cater to every kind of implementation/platform may not be readily available.

The key here is to know when to go for white box testing. Depending on the maturity of the system in question, the tester’s experience with the system, and whether you’re at early stages of a product lifecycle or trying to improve code quality, your decision will vary. if aren’t familiar with white box testing you can consult a cybersecurity company like Khanna Security Solution Pvt Ltd. In order to check for vulnerabilities in your company’s digital asset which can prove to be harmful for your organization.

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One thought on “White Box Testing

  1. your blog are really helpful for all testers and beginners.this all provided knowledge are unique than other testing blog.WHITE BOX TESTING are lovely explain.
    keep updating,Thanks

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