Unit testing is granular software testing performed on a single function of an application. It is named after the smallest testable part of the code, “the unit.” Unit testing is usually done independently, without considering other functions that depend on the unit being tested.

For example, developers write a unit or module of source code dedicated to an application’s Delete functionality. They would also write codes for other functions, such as Undo Delete, Upload Image, and Add Text. Some of the functions, like Undo Delete, may depend on the Delete function or source code unit. But during unit testing, only the Delete function will be tested to make sure there is no problem with the code. Testing the Undo Delete function will require a separate unit test.

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Read More about a “Unit Testing”

Like other types of software testing, unit testing aims to detect flaws in the source code before deployment. Unit testing does this by focusing on individual units of source codes instead of testing the entire software.

Unit testing is like taking a whole Lego set and examining one piece closely to ensure that it has the correct dimensions. Ultimately, the process helps ensure that every piece fits the Lego set perfectly. In the same way, unit testing, although granular, helps make sure that the whole application or software works properly. If there is any defect in a particular unit or function, it is immediately detected and fixed before end users encounter errors.

What Are the Methods of Unit Testing?

Unit testing can be done in different ways, depending on the test’s goal and the functions being tested. Below are three common techniques used in unit testing.

What Is White-Box Testing?

In white-box testing, only the function’s behavior is tested. The tester knows how the functionality is supposed to work, which is why it’s called “white box” or “glass box.” The tester asks questions like, “Does the Upload function call the Choose File window?” or “Will the Delete functionality remove the file permanently?” If a function is not working the way it should, the tester reports it as a bug.

What Is Black-Box Testing?

Black-box testing is a unit testing technique that tests the application’s functions through the user interface (UI). It aims to answer questions like, “What happens when I click the Upload button?” or “What happens to a file when deleted?” It’s quite similar to white-box testing, but in black-box testing, the tester is not aware of how the function is internally structured and instead takes note of the behaviors they encounter while testing.

What Is Gray-Box Testing?

Gray-box testing is a cross between white- and black-box testing. You can think of it as a semi-tinted glass box, wherein the tester partially knows how the functions are internally designed. However, they don’t have a deep understanding of the unit, unlike in white-box testing. For example, testers are aware that the Delete functionality will remove the file from the application. Still, they don’t know if the file is permanently removed from the server or stored for a definite period.

What Are the Benefits of Unit Testing?

Knowing what unit testing is helps us understand how important it is to the software development process. It unveils problems with the source code that could otherwise remain undetected. Specifically, this type of testing has the following benefits to the development team and the whole company:

  • Cost reduction: Unit testing results in the early detection and mitigation of bugs, so they won’t have significant and costly effects on the entire software.
  • Scalability: Unit testing allows for greater scalability with fewer defects in the code. New features and functionalities can be added without worrying too much about bugs affecting the application’s usability.
  • Reusable code: Since unit testing reduces bugs, the specific unit of the source code can be reused. That helps save time and hastens the release of the software product.
  • Reliable documentation: Unit testing helps build test cases that are run every time changes are made to the code.

Software development is an intricate undertaking that involves several processes, including unit testing. The applications we use on our computers or mobile phones underwent sophisticated and in-depth testing before they were released and made available for our use.