White Box vs Black Box Testing

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Software testing is a process of analyzing a system to identify any errors, gaps, or missing requirements versus the actual requirement. When it comes to types of testing, we have two different major types of testing – White Box testing and Black Box testing. White Box testing generally involves testing based on an inner knowledge structure and design of the system. On the other hand, when it comes to Black Box testing, this is also known as functional testing, and it is performed without knowledge of the inner workings of the system. In this article, I will discuss in detail White Box testing vs Black Box testing covering their key differences.


What is Black Box Testing?

Black Box testing is a software testing method that examines the functionality of an application without having knowledge of internal code structure. So, you will be testing on a UI or public interface. Also, the major focus of the black box testing is with the output, wherein you are given a set of inputs to the application, which will result in the output.

Below are the steps to perform Black Box testing:

  • Firstly, when the requirement is given, the tester will start analyzing the client’s requirements and needs.
  • Before writing the test cases, the tester will do some ad-hoc testing to get the valid and invalid scenarios.
  • In the next step, the identified scenarios need to be documented, and that needs to be converted as test cases.
  • Execute the test cases developed, but you will start the execution only when the developer deploys the code.
  • Next, you need to verify the output with the expected result. While execution, you will get to know with the valid and invalid inputs what exactly matches the expected result.
  • If it is not matching with the expected result, then you will log it as an issue.


In Black Box testing, we have two different testing types: functional testing and non-functional testing. And also, some of them consider regression testing as another type of Black Box testing. When it comes to functional testing, the Black Box testing type is related to the functional requirement of the system. It is done by the software testers majorly. So, these types of testing will be considered as a part of functional testing where we will verify the functionality of the application.

When it comes to non-functional testing, it is a type of Black Box testing which is not related to testing of specific functionality. Non-functional requirements are entirely related to the application’s performance, such as the application’s usability, security, compatibility. For example, performance testing, usability testing, security testing.


What is White Box Testing?

White Box testing is a technique that examines the program structure or design and with program logic or the code. This testing technique mainly verifies and tests the working code. This type is testing is as known as clear box testing, open box testing, transparent box testing, code basic testing, glass box testing.

Below are the reasons to perform Whitebox testing:

  • To check the internal structure
  • To verify the broken or poorly structured parts in the coding process
  • To identify the working flow of an application
  • To check expected output is coming
  • Testing of each of the statement
  • Testing of object
  • Testing of function on an individual basis

We have specific techniques in white box testing which are used to test the code. They are statement coverage, branch coverage, and path coverage. First is statement coverage, where each statement written by the developer will be tested line by line. In branch coverage, all the branches like if statements, which conditions and loops will be tested. And in path coverage, all possible paths, which means that each statement and branch is covered and tested.

White Box vs Black Box Testing: Key differences


The first difference is basically around who does what sort of testing. Black Box testing is typically done by software testers. If there is help required from other team members like developers, they also can help, but most of the time, Black Box testing is done by software testers or the testing team.

White Box testing is mostly done by developers. If the tester has a good understanding of the White Box testing and programming knowledge, only then QA team can cover white box testing. In most organizations, you will see that only developers do White Box testing.

Scope of Testing

In Black Box testing, as a tester, you usually verify the functionality without worrying about the internal structure of the code. So, if you are doing Black Box testing, you don’t need to worry about how the internal code is working or what all methods and classes are being written, or how the overall code is being called internally.

In White Box testing, the knowledge of internal code implementation is required because, in White Box testing, your testing is not limited to just working of functionality, for example, clicking on the link and verifying that the page is getting open successfully. In White Box testing, the testing will actually be around the coverage of the code that has been written to implement the functionality. So, in the White Box testing, when functionality is invoked, you will verify what all methods are being called and whether with the test cases applied, all the permutation combination or all the scenarios statement coverage or the conditions or loop coverage has been done or not. So that is why knowledge of the internal code implementation is required if you want to test the internal working of the code.

Functional vs Structural Testing

Black box testing is also functional testing. In Black Box testing, you verify the functionality or the requirement that is being implemented into the application. So, for example, a simple registration functionality to test, if the user is getting registered properly or adding the items to the cart in an e-commerce website and then checking out to make the payment, so just verifying the adding item’s functionality, checking out functionality, payment functionality, etc. So, in the black Box testing, you are just verifying the functional aspect of the testing.

White Box testing is the structural verification which is mainly for the actual design document. So, when the technical architect does the high-level design and the detailed design, that design must do structural testing. Then, based on whatever design has been done, the code structure needs to be tested, the statements need to be tested, and how all the methods and classes are being structured and modularized.

Programming Knowledge

In the Black Box testing, no programming knowledge is required because you don’t need to understand what happens internally. For example, when you click on the register link, you just need to verify if the registration page is opening correctly or not in the Black Box testing. So, you don’t need any internal code structure knowledge or how the code has been deployed or developed in Black Box testing.

But if it comes to White Box testing, it requires programming knowledge because you need to get into the code and use the testing frameworks to basically write the test cases. Also, you need to understand the code coverage tools that you can utilize and run the unit tests or the test cases that you have written in the unit test tools to basically verify the coverage. So, if the application has been developed using Java, you need the understanding of the java programming language, if it is developed using python, you need to understand the python testing frameworks and the knowledge of the python programming language. So that is why developers perform White Box testing because they have good programming knowledge.

Time Consumption

Time consumption in Black Box testing depends upon the availability of the functional specifications.

White Box testing takes a long time to design test cases due to lengthy code. In addition, it is time-consuming as the complete internal code structure is tested.

Common Testing Techniques

Below are the testing techniques used in White Box testing:

  • Control flow testing
  • Data flow testing
  • Branch testing
  • Path testing
  • Statement coverage
  • Decision coverage

Below are the testing techniques used in Black Box testing:

  • Decision table testing
  • All-pairs testing
  • Equivalence partitioning
  • Boundary value analysis
  • Cause–effect graph
  • Error guessing

The table below summarizes the differences between White Box and Black Box testing:

White Box Testing Black Box Testing
It is a testing approach that requires internal code knowledge of the software It is a testing approach which is used to test the software without the knowledge of internal structure of the application
It is mostly performed by software developers It is mostly performed by software testers
The focus of this testing is to understand how the application is built The focus of this testing is to understand stand how the application is working
Programming and implementation knowledge is required in this testing Programming and implementation knowledge is not required in this testing
It is the structural test of the software It is the functional test of the software
It is more time consuming and exhaustive It is less time consuming and exhaustive
It is used for low-level testing such as unit testing, integration testing. It is used for high-level testing such as system testing, acceptance testing.
Best suited for algorithm testing Not suited for algorithm testing
This testing requires the code access This testing does not require any code access
Errors in the software can be detected early Errors are identified only once the code is deployed


Final Thoughts

So that was all about the key differences between Black Box testing and White Box testing. We cannot say that Black Box testing is more important or White Box testing is crucial.  Both types of testing are very important to deliver quality software successfully. Developers are more focused on White Box testing, and the testers are more focused on Black Box testing. Using these testing types, you can ensure to find the maximum defects in the application, which will help improve the application’s efficiency.

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