What is white box testing?

White box testing is a complex form of testing used in software development. Often going by other names, including transparent box testing, open box testing, code-based testing, and glass box testing. As all of these names suggest, white box testing includes a process of “looking behind” elements to see what is going on underneath. 

White box testing can be a trickier topic to get your head around in testing. So, in this blog, let’s shed some light on it for you.

What is white box testing used for?

Testers perform white box testing in order to inspect and verify the internal workings of software. It is a process often automated and used to get a comprehensive picture of what is happening under the hood of a piece of software. Components that are tested include coding, design, infrastructure, usability, security, and so on. Rather than focusing on simply the functionality of software, it is a process also testing the entire workings of the software. 

White box testing can be seen in comparison to black box testing, a topic on which we have another explanatory blog for you to check out. Black box testing focuses on functionality, by providing input to a system and observing the output. In this form of testing, no knowledge of internal systems is required, it is a more surface layer form of testing. 

Whether white or black box testing models are chosen depends on the requirements, scope, and even budget of a project. It can also depend on the expertise and experience of the testers involved, as white box testing is a more advanced development technique. 

All forms of testing have the same basic premise, to test whether something works or not. White box testing goes a little further to help us understand why a bug may occur and on what level. 

The pros and cons of white box testing

When it comes time to decide on what kind of testing is appropriate for a given project, it is a good idea to look at the pros and cons of each model. The following are the main advantages and disadvantages of the white Box approach:


Complete code coverage: White box testing is a very thorough approach to testing as all code paths can be covered and inspected. It is much easier to find hidden bugs and errors when such a comprehensive approach to testing is taken. Ultimately, this saves time and money down the line and may prevent cyber attacks even at the early stages of development.

Easy to automate: White box testing is often seen in continuous integration/continuous delivery (CI/CD) development and it is something that can be easily automated, however, it will take expertise and a strong budget to do so. With automation, more continuous improvement can be made and developers and testers will more easily be on the same page.

Code optimisation: It is easy for extra lines of code, bugs, and any other mishaps in code through white box testing. Getting down to this deeper layer of the software can help everything run much more smoothly for the rest of the project and helps to finetune the developers’ processes. 


Requires an expert hand: White box testing is complex and, especially if automated, will require an expert tester to carry out. This can involve hiring someone pretty expensive for your project and dealing with internal hiring processes, costing both time and money. 

Time-consuming for larger projects: It can take a lot of time to carry out white box testing and to rewrite code when errors are flagged by the process. If you have a large project with many features and components, you may find that white box testing racks up quite a bill as it requires many man hours over time. 

User experience/functionality untested: When used alone, white box testing does not allow you to consider how a piece of software is currently able to be used and experienced by your target user. While you can consider how well the code is functioning and whether the security is ironclad or not, you can’t decipher whether the product is enjoyable or usable by the consumer. This implies that a multifaceted approach to testing needs to be considered for a full scope of perspective. 

Wrapping up

Overall, white box testing is a tricky but impressive testing beast. It is a testing approach that allows an expert tester to dive deeply into the layers of software and figure out where there needs to be tweaks and improvements. When used in the right hands, the testing approach can build a high-quality end product with tight security and impressive code. 

White box testing is not something designed with user requirements in mind, this is the realm of black box testing. With the approach detailed in this blog, we are looking at the finer details of code and infrastructure rather than how a product is to be experienced by a real-life person. 

As with everything, there are disadvantages and advantages to be had here. White box testing can be expensive and time-consuming, but it can also produce optimised results and can be easily automated in continuous development.  

What kind of testing do you need? Consulting a bespoke software development company may be your best way forward. 

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