Black Box Testing vs White Box Testing – What they are and which to choose?

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Flawless software can’t be developed without thorough testing to ensure optimum quality. And, when it comes to software testing, Black Box Testing and White Box Testing are two of the most popular methods.

Software testing is a huge playing field, i.e., there are various ways to do it, depending upon the requirements of the developer and the end-users. Either way, proper software testing ensures substantial savings for the developing firm. It drives customer satisfaction resulting in better ROI.

Testing automation or adherence to KISS principles are some of the emerging trends of the industry. For the best outcomes, the developer should have a sound idea of which to use and when.

In this blog, we discuss White Box and Black Box Testing, explaining what they are, how they are different, and when to use them.

What is Black Box Testing?
Based entirely on the specificity of the software at hand, Black Box Testing is a sort of ‘external’ method of testing. For this, the developer doesn’t need to use processes that analyze the internal structure or functioning of the code.
In layman’s terms, Black Box Testing focuses only on the input and output of the software. Thus, it’s also known as data-driven testing.

Using the various Black Box Testing techniques, one checks the functionalities of the application. The best part of doing this is that the tester doesn’t necessarily have to be a software expert. It’s enough to go through the software thoroughly, checking whether the interface or the other functionalities are running as smoothly as desired. That is, there’s no need to check the code in Black Box Testing.

Although this method is a test for gauging the experience of the end-user, there are three major ways of doing it.

1. Equivalence Class Testing – This method involves the categorization of test cases, eventually reducing the number of trials required.

2. Boundary Value Analysis – Here, the developer tests for threshold values that are likely to generate errors.

3. Decision Table Testing – For this, the developer deliberately puts error-inducing inputs and checks for the result.

What is White Box Testing?
As the name suggests, White Box Testing is a highly transparent method of software testing. Contrary to its counterpart, this method tests the internal functioning of the software. Starting from the design to the code used for building software to the internal pathways, White Box testing looks at everything.

That is, it goes beyond just seeing whether the software is running smoothly. Due to the extra degree of diligence used in White Box testing, developers using this mechanism need to be fully aware of the technology, software programs, and other technical aspects. Indeed, this method is the most detailed of the various testing methods available.

This method can be performed in the following ways:

Covering of Statements – This checks every line of code and doesn’t leave anything to chance.

Covering of Branches – Rather than a line-to-line test, this method checks the various branches in the software’s source code.

Black Box Testing vs White Box Testing – Differences that Matter
With a basic understanding of what these processes are, we can now outline the major instances in which the two differ.

Phase of Implementation
One of the most striking differences, when it comes to the White Box Testing vs the Black Box Testing argument, is the fact that the former can be performed even before the software’s completion. It’s the perfect way to test software in the initial phases of development or at any stage after that. Doing so informs the developer of not only the existing errors but also future events that may occur due to the given code or pathway.

Black Box testing, on the contrary, can be performed only when the development is complete as it involves testing of the interface.

Difference in Results
As discussed above, Black Box testing is best suited in a scenario when the software program is complete. The results of Black Box testing have to be thoroughly analyzed as it doesn’t check codes, their structures, and pathways.

On the other hand, white box testing gives the developer a clear picture of the internal functioning, enabling a detailed analysis of the codes. It helps in identifying syntax errors, as well as design errors.

Degree of Expertise
Black Box Testing is preferred by many since a lot can be achieved by this trial and error method. However, White Box Testing can be performed only by expert developers who have a sound knowledge of the program and programming languages. Moreover, the process is quite time-consuming and lengthy.

White Box Testing vs Black Box Testing – Which one is better?
Developers are often found using a hybrid of the two. Both have advantages and disadvantages. Thus, they are both equally important and play a complementary role in software development.

White Box Testing in the early stages of software development lays the strong foundation for Black Box testing after completion. Together, they ensure that the final product has the best possible performance, interface, and other functionalities. A holistic quality assurance that adequately benefits both the owner and users of software is possible only through a combination of Black Box Testing and White Box Testing.

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