When it comes to software testing, there are two main types: white box testing and black box testing. While these terms may seem pretty self-explanatory, the differences between white box testing and black box testing can be a bit more subtle than you might think.
Both of these testing methods are used to identify different types of bugs in the software being tested, with each one tackling that task from a different angle.
Testing is typically performed for one of two reasons: to find bugs or to verify code. Each style of testing helps you meet your testing objective by focusing on a specific kind of error.
Depending on how your code is organized (and what its individual functions/responsibilities are), you’ll want to choose one test over another so you can uncover the type of issues you need to find as quickly as possible.
What is White Box Testing?
White box testing, or structural testing, is any testing method where the tester knows the internal structure of the software/system under test.
This includes information about the design of the system, programming languages used and their syntax, code structures, and data tables.
Structural testing is often performed by developers themselves, but can also be done by testers with extensive knowledge of the architecture of the system.
White box testing often focuses on testing the code itself (the syntax, modules, and other programming elements).
One of the main goals of white box testing is to test the code’s “expansion” during execution.
This means you’re looking at how the code is executed and how it’s going to be executed. You have access to the code, so you can see where it all unfolds when the program is being used. White box testing is often broken down into three types of code testing:
What is Black Box Testing?
Black box testing, or functional testing, is any testing method where the tester has no knowledge of the internal structure or implementation of the system under test.
In other words, the tester has no knowledge of the code or programming languages used in the software. This is often done by testers/assessors who don’t have any prior knowledge of the project’s architecture.
Black box testing often focuses on testing the functionality of the product being tested (as opposed to the code). Black box testing is often broken down into three types of testing:
Differences Between White Box Testing and Black Box Testing
Besides the obvious fact that one tests the code while the other tests the functionality, there are a number of other key differences between white box testing and black box testing:
Code-based bugs vs. functionality bugs – White box testing is designed to test the syntax of the code and look for bugs related to the code itself.
Black box testing is designed to test the functionality of the software/application and look for bugs related to the software’s ability to function as expected.
Test coverage – White box testing focuses on test coverage in terms of how the code will be executed. What does the code do, when does it do it, and how does it execute? Black box testing focuses on test coverage in terms of the functionality of the product.
How does the software/app do what it’s supposed to do? Internal vs. external perspective – White box testing takes an “internal” perspective on testing.
You’re looking at the code itself, its elements, and how it operates as it’s being executed. Black box testing takes an “external” perspective. You’re looking at the functionality of the application from an end user’s point of view.
When to Use Black Box Testing
Black box testing is the best method to use when you have no access to the source code of the software/application that you’re testing.
Black box testing is often used to test applications that have been integrated with other systems that you have no control over.
It’s also used to assess applications where the developer has prohibited you from accessing the source code (such as with closed source systems).
Black box testing is also used when you’re dealing with a system/application that has a particularly unusual or non-standard layout.
In these cases, it may be easier to test from an outside perspective since you don’t have to know the specifics of the application. You can just work with the functionality and the end user experience. Black box testing is useful for testing any type of application/software, although it’s most commonly used for testing web-based systems. It can also be used to test non-software systems, like robotics.
When to Use White Box Testing
White box testing is the ideal testing method when you have access to the source code of the software/application that you’re testing. This testing style often works best when it comes to testing code that you’ve written yourself.
You know what you’re trying to test, you know how the code works, and you have a clear understanding of what you’re looking for when you’re testing the application.
White box testing is also used when you’re testing a system where the architecture is well-documented or there are clear design/architecture diagrams available that you can follow. In these situations, it may be easier to test from an internal perspective since you have access to all of the information you need to thoroughly test the system.
Summing up
While white box testing and black box testing are both valid testing methods, they have different focuses. White box testing focuses on testing the code itself, while black box testing focuses on testing the functionality of the application.
If you’re testing an application where the source code is off-limits, you may want to employ black box testing. If you’re testing an application where you have full access to the source code, white box testing is a good choice.
