What Is White Box Testing? Techniques, Types, Pros and Cons

What Is White Box Testing? Techniques, Types, Pros and Cons
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White Box Testing is a testing technique in which software’s internal structure, design, and coding are tested to verify input-output flow and improve design, usability, and security. In white box testing, code is visible to testers, so it is also called Clear box testing, Open box testing, Transparent box testing, Code-based testing, and Glass box testing.

It is one of two parts of the Box Testing approach to software testing. Its counterpart, Blackbox testing, involves testing from an external or end-user perspective. On the other hand, white-box testing in software engineering is based on the inner workings of an application and revolves around internal testing.

The term “White” was used because of the see-through box concept. The clear box or WhiteBox name symbolizes the ability to see through the software’s outer shell (or “box”) into its inner workings. Likewise, the “black box” in “Black Box Testing” symbolizes not being able to see the inner workings of the software so that only the end-user experience can be tested.

Features of white box testing:

Features of white box testing:
  1. Code coverage analysis: White box testing helps to analyze the code coverage of an application, which helps to identify the areas of the code that are not being tested.
  2. Access to the source code: White box testing requires access to the application’s source code, which makes it possible to test individual functions, methods, and modules.
  3. Knowledge of programming languages: Testers performing white box testing must have knowledge of programming languages like Java, C++, Python, and PHP to understand the code structure and write tests.
  4. Identifying logical errors: White box testing helps to identify logical errors in the code, such as infinite loops or incorrect conditional statements.
  5. Integration testing: White box testing is useful for integration testing, as it allows testers to verify that the different components of an application are working together as expected.
  6. Unit testing: White box testing is also used for unit testing, which involves testing individual units of code to ensure that they are working correctly.
  7. Optimization of code: White box testing can help to optimize the code by identifying any performance issues, redundant code, or other areas that can be improved.
  8. Security testing: White box testing can also be used for security testing, as it allows testers to identify any vulnerabilities in the application’s code.

Types of White Box Testing

White box testing encompasses several testing types used to evaluate the usability of an application, block of code, or specific software package. They are listed below —

  • Unit Testing: It is often the first type of testing done on an application. Unit Testing is performed on each unit or block of code as it is developed. Unit Testing is essentially done by the programmer. As a software developer, you develop a few lines of code, a single function, or an object, and test it to make sure it works before continuing Unit Testing helps identify a majority of bugs, early in the software development lifecycle. Bugs identified in this stage are cheaper and easy to fix.
  • Testing for Memory Leaks: Memory leaks are the leading causes of slower-running applications. A QA specialist who is experienced in detecting memory leaks is essential in cases where you have a slow-running software application.

Apart from the above, a few testing types are part of both black-box and white-box testing. They are listed below

  • White Box Penetration Testing: In this testing, the tester/developer has full information on 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 Mutation Testing: Mutation testing is often used to discover the best coding techniques to use for expanding a software solution.

White Box Testing Tools

Below is a list of top white box testing tools.

  • EclEmma
  • NUnit
  • PyUnit
  • HTMLUnit
  • CppUnit

How do you perform White Box Testing?

We have divided it into two basic steps to give you a simplified explanation of white box testing. This is what testers do when testing an application using the white box testing technique:


The first thing a tester will often do is learn and understand the source code of the application. Since white box testing involves the testing of the inner workings of an application, the tester must be very knowledgeable in the programming languages used in the applications they are testing. Also, the testing person must be highly aware of secure coding practices. Security is often one of the primary objectives of testing software. The tester should be able to find security issues and prevent attacks from hackers and naive users who might inject malicious code into the application either knowingly or unknowingly.


The second basic step to white box testing involves testing the application’s source code for proper flow and structure. One way is by writing more code to test the application’s source code. The tester will develop little tests for each process or series of processes in the application. This method requires that the tester must have intimate knowledge of the code and is often done by the developer. Other methods include Manual Testing, trial, and error testing, and the use of testing tools as we will explain further in this article.

White Box Testing Techniques

White Box Testing Techniques

White-box testing requires a more in-depth knowledge of code structure and is more resource-intensive than black-box testing, making this methodology ideal for software systems that are mission-critical to an enterprise (for instance, banking apps or internet security systems that must function seamlessly) that must remain bug-free.

Testers employing this approach must possess extensive knowledge of programming languages to comprehend how an application operates and develop effective tests for it. Furthermore, testers must possess a deep understanding of code layout to detect any potential logical errors such as infinite loops or incorrect conditional statements that might arise during testing.

Some of the most widely used white box testing techniques include statement coverage, branch coverage, and path coverage. With statement coverage, testers verify whether all statements in a program have been covered by its unit test suite; with branch coverage and path coverage they map code into different branches with conditional logic so each path is tested by unit tests; while path coverage evaluates functionality within an application.

1. Statement Coverage

White-box testing can help identify errors in software systems that would otherwise remain undetected using traditional black-box or gray-box testing methods. By comparing its actual outputs against its intended ones, this testing technique helps uncover any bugs that might otherwise go undetected.

Statement coverage is a measure used to track how many statements in a program have been executed; this technique can be employed as part of white box testing to verify that all code included in their test cases has been thoroughly explored and exercised. It provides developers and testers with an effective means of assuring all their test cases have been fully executed and exercised properly.

Testing software code requires time and expertise. Furthermore, hiring professional testers to conduct this testing may prove expensive; but this type of testing is essential in making sure your software functions as intended and doesn’t contain any hidden bugs; also useful when trying to determine any mismatch between requirements or specifications and implemented code.

2. Branch Coverage

White box testing (also referred to as structural or code-based testing) involves developing test cases that examine an application’s internal logic and flow, giving you access to testing it without needing a user interface (UI) and starting testing very early in its development cycle.

White box testing seeks to cover every possible path through an application by measuring branch coverage – this compares executed branches against all possible pathways and represents how exhaustive testing was done. As branch coverage measures this aspect of testing, higher numbers indicate more thorough tests.

There are various approaches to testing branch coverage, such as path checking, loop testing, and data flow testing. Path checking evaluates all possible inputs into a function and verifies that its output matches expectations; loop testing evaluates single loops, concatenated loops, and nested loops for efficiency, conditional logic, and proper handling of variables; while data flow testing follows variables through execution paths of an application to ensure they’re being properly initialized or not being incorrectly handled by variables declared as declared but never used or initially initialized incorrectly or improperly handled variables.

3. Path Coverage

White box testing not only detects errors at the code level but also ensures all possible paths have been covered, helping identify any wrong-doing sequences of actions during program flow and ultimately improving overall system performance.

White box testing often takes the form of unit testing, which involves verifying each procedure within an application’s source code by creating and running test cases. Developers tend to perform this type of white box testing as it requires an in-depth knowledge of its functionality.

White box testing can also be utilized during integration and system tests and is used to detect problems caused by mismatched specifications or design weaknesses in software. White box tests evaluate internal variables that lead to outputs as well as any issues with coding that arise, such as whether loops are closed or infinite; additionally, it tests for security vulnerabilities by observing how different types of data input are handled by programs; manual or automated static analysis tools are both viable methods of conducting white box tests.

Advantages of White Box Testing

  • Code optimization by finding hidden errors.
  • White box test cases can be easily automated.
  • Testing is more thorough as all code paths are usually covered.
  • Testing can start early in SDLC even if GUI is not available.

Disadvantages of WhiteBox Testing

  • White box testing can be quite complex and expensive.
  • Developers who usually execute white box test cases detest it. The white box testing by developers is not detailed and can lead to production errors.
  • White box testing requires professional resources with a detailed understanding of programming and implementation.
  • White-box testing is time-consuming, bigger programming applications take the time to test fully.

Black Box vs White Box vs Gray Box Testing

Black-and-white box testing techniques often spark debate within software security circles. Bret Pettichord, CEO of SonarQube, describes white box tests as more effective and can be automated, yet also time-consuming and expensive to execute. Due to their lower-level nature, white box tests can easily integrate into CI/CD pipelines while providing developers with immediate feedback on their code; making them integral parts of secure DevOps workflows.

Gray box testing (also referred to as translucent or transparent box testing) is a hybrid between white-box testing and black-box methods, drawing from both for their effectiveness. It involves a limited understanding of an application’s inner working structure while simulating an insider attack or breach from an external attacker’s perspective to detect vulnerabilities and discover vulnerabilities.

Key elements of this approach are flow graphs for identifying all possible paths and test cases to verify each one, leading to higher statement coverage which guarantees every executable code path has been tested.


  • White box testing can be quite complex. The complexity involved has a lot to do with the application being tested. A small application that performs a single simple operation could be white box tested in a few minutes, while larger programming applications take days, weeks, and even longer to fully test.
  • White box testing in software testing should be done on a software application as it is being developed after it is written and again after each modification.

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