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White Box Testing – Pros and Cons


In the past couple of blogs, we have been delving deeper into penetration testing, a process in which a cybersecurity expert or a team of experts execute a controlled and authorized attack against the security infrastructure. We have touched upon how it works, its importance and the different types of pen tests such as white box penetration testing, black box testing and grey box testing. 

In this article, we will focus on white box penetration testing. White box or precise box testing is a testing technique in which the internal structure, internal designs, and code structure are analyzed. The term white box penetration testing was used because of the see-through box concept. The name white box symbolizes the ability to see through the software’s outer shell (clear or open box) into its inner workings (code, functionality, mechanism, process flow, etc.).

In white box penetration testing, the tester/developer has complete information of the application’s source code, detailed network information, IP addresses involved and all server information the application runs on. The aim is to attack the code from several angles to expose security threats.

White box penetration testing involves testing the internal code to find security holes, strengthening security by improving design and usability, and correcting poorly structured paths in the development process. It involves checking several defined inputs against expected outputs. This process helps in identifying security risks or bugs as fast as possible. 

Before we go into the pros and cons of white box penetration testing, we need to understand the types of white box penetration testing, which includes:

  • Unit Testing: A test is performed on every single unit or code block as it is being developed. A software engineer identifies the security risks or bugs in the early stages and can be fixed easily.

  • Integration Testing: This type of open box testing involves combining individual units or components of the application’s source code and testing them as a group. The purpose is to expose errors in the interactions of the different interfaces with one another. It takes place after unit testing. 

  • Regression testing. In regression testing, the penetration tester does a rerun of the tests, checking if the old code works after the new bug fixes and changes are made, ensuring that the changes have not adversely impacted the existing functionalities. 

The advantages of white box testing:

  • The transparency of this type of testing allows the testing to be extensive, as the tester can do comprehensive tests covering all the paths and testing the entire structure and code base. It also assesses internal and external vulnerabilities that could help avoid future security threats and attacks. 

  • Less time to perform white box testing – While the time required to perform white box testing may become a con when it comes to an extensive, complex application, which we mention later in the blog, but when all the available information about the application is available, it takes less time for the tester to go in, understand the code swiftly and perform the checks, but with large applications with complex functionalities, the testing can run into weeks or months. 

  • The test cases can be easily automated, and many tools are available for performing automation, which expedites these tasks.

  • Code optimization – White box testing helps remove extra lines of code and identify hidden errors. There is a higher chance of detecting security risks or bugs due to all the information available about the application. 

  • The process of white box testing can start early in the Software Development Lifecycle Process (SDLC), even before the user interface comes about. This gives the developer a chance to fix the bugs early on or add elements to improve security in the early stages of the development process.  

  • No requirement of an interface as is needed in other types of testing, such as black box testing. 

The disadvantages of white box testing:

  • Certain functionalities could be missed out as only the available code is tested.

  • Many developers are against it as it is a tedious process.

  • It is very time-consuming as the codes must be redesigned along with test cases that need to be rewritten. 

  • Requires resources and professional skills as testers with in-depth programming skills are necessary, unlike in black box testing. In white box testing, a tester is expected to understand the mechanism of the codebase of the application and have strong programming language knowledge. 


White box penetration testing should be conducted on a software application as it is being developed, after it is written, and again after each modification. This process can be very complex and time-consuming, depending on the size and expanse of the application being tested. In our earlier blog on ‘Black-Box vs Grey-Box vs White-Box Penetration Testing,’ we had explained what type of testing would be best suitable for your organization. Each has its strengths and weaknesses in speed, accuracy, coverage and efficiency.