White Box Testing in Software Engineering

white box testing

What is White Box Testing?

White Box Testing is type of testing in which software solution’s internal structure, coding and design is tested. In this type of software testing, the code is easily visible to the tester. It focuses mainly on verifying the flow of inputs and outputs throughout the application, tries improving design, usability and strengthening the security. This testing is also called as Clear Box testing, Structural testing, Open Box testing, Transparent Box testing, Code-Based testing, and Glass Box testing. It is usually performed by professional developers.

It is 1 of 2 parts of the “Box Testing” approach used in software engineering. Its otherpart is Blackbox testing which involves testing from any end-user type perspective. On the other hand, This Whitebox testing is based on all the inner workings of any desired application and revolves around the internal testing.

The term “WhiteBox” was used in this testing because of the visible box concept. The clear box or the WhiteBox name basically symbolizes the ability of seeing through the software’s outer layer (or the “box”) into its all the inner workings.

What do you verify in the White Box Testing?

White box testing involves all the testing of software code for the below mentioned:

  • Holes in internal security
  • Broken structured paths in the coding processes
  • The flow of any specific inputs through the code
  • Expected output
  • The functionality of any conditional loops
  • Testing of all the statement, function and object on an individual basis

The testing can be easily done at system, integration and the unit levels of software development. One of the most basic goals of the whitebox testing is to verify any working flow for desired application. It also involves testing a particular series of predefined inputs against the expected or desired outputs so that when any specific input does not result into the expected output, you have surely encountered a bug.

How do you perform White Box Testing?

To give you a basic simplified explanation of the white box testing, we have divided it into parts i.e two basic steps. This is about what testers do when they perform any testing on application by using the white box testing technique:


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


The second most basic step for white box testing involves the testing of application’s source code for the proper flow and structure. One way is by writing more and more code to test the desired application’s source code. The tester will itself develop little tests for every process in the application. This method of testing requires the tester that it must have intimate knowledge of the source code and is often performed by the developer. Other methods of testing include Manual Testing, trial, and the error testing and use of testing tools.

White Box Testing Techniques

A major type of White box testing technique is known as Code Coverage analysis. Code Coverage analysis eliminates all the gaps in a Test Case suite. It usually identifies all the areas of a program that are not perfectly exercised by a set of test cases. Once all the gaps are identified, you can create test cases to verify the untested parts of the code. It results in increasing the quality of software product.

There are many automated tools available in order to perform Code coverage analysis. Below are few coverage analysis techniques used –

Statement Coverage:- This type of technique requires all the possible statement in the code that is to be tested at least 1 time during the testing process of the software engineering.

Branch Coverage – This type of technique checks every possible way (if-else and any other conditional loops) of the software application.

Apart from the above types, there are many coverage types such as the Condition Coverage, Path Coverage, Multiple Condition Coverage, Function Coverage etc. Each type of technique has its merits and it attempts to test (cover) all the parts of software code. Using the Statement and Branch coverage you can generally attain upto 80-90% code coverage which is quite sufficient.

Types of White Box Testing

White box testing encompasses several types of testing that is used to evaluate the usability of an application, blocking of code or any specific software package. These are listed below —

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

Apart from the above types, a few more testing types that are part of both black box and the white box testing-

  • White Box Penetration Testing: In this kind of testing, the tester/developer has complete information of the desired application’s source code, IP addresses, detailed network information involved and all the server information on which the application runs on.  The main aim is to attack the code from many angles to expose the security threats.
  • White Box Mutation Testing: The Mutation testing is used to discover the best coding method that can be used for expanding a software solution.

Some White Box Testing Tools

Below is a list of the top white box testing tools.

  • Veracode
  • EclEmma
  • NUnit
  • JSUnit
  • JUnit
  • CppUnit

Advantages of this Testing

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

Disadvantages of this Testing

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



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