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Software Development and Software Testing

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What is Unit Testing? Types, Pros, Cons and Best Tools

Posted in Software Development, Software Testing
What is Unit Testing

Software development involves many phases and steps, from writing code and testing each function to debugging, and deploying.

How can you check whether a software product is defect-free and consistent with relevant requirements? Unit testing is one critical way. Today, almost every software development company includes unit testing in its software testing cycle to ensure that every unit of the software product is fully functional and performs as expected.

Today we’ll cover exactly the unit testing definition along with its features, importance, advantages and disadvantages, and best practices.

What is Unit Testing?

Unit testing is at the top of the testing pyramid, meaning it’s the first level of functional testing — the most critical step in developing an error-free software product. The main goal of unit testing is to test each unit or module of the product at the early stage of development to prevent any errors from migrating to the next level.

First thing’s first: what is the definition of the unit? Here, a unit is the smallest and simplest part of the product that you can test to improve its performance. It can be a method, procedure, object, or module. This test only requires a few inputs and generates a single output.

Both web developers and quality analysts are often responsible for performing unit testing either manually or through automation (most common).

Unit testing helps companies:

  • Improve code quality
  • Create reusable modules
  • Simplify documentation
  • Ensure seamless integration with several tools and technologies

unit testing advantages

What Does Unit Testing Do?

Unit testing comes with several functions that help you improve the functioning of your software product. Some unit testing functions include:

  • Creates the foundation of extensive programming because of its reliability of unit test frameworks.
  • Helps you to evaluate each unit of the software product seamlessly.
  • Helps you leverage simple testing techniques, such as walk-through, review & inspection of programming code.
  • Ensures adherence to strict test plans for each isolated unit to generate effective results.
  • Properly conducting unit testing will save your time and money in finding and resolving errors at a later complex stage

Importance of Using Unit Testing

Unit testing helps developers design robust software components to maintain sound code to eliminate any issues in each code unit. When creating any product or software, it is essential to find and fix potential defects in the early stages of the software development cycle (SDLC).

Unit testing serves as the foundational check to ensure that the software product meets the specified requirements and behaves as expected. When unit testing is performed correctly, it helps companies save time and money. We’ll touch upon some more specific advantages later on in this article.

Unit testing is an integral part of every agile software development process. For every software build, developers should execute the unit test suite to generate a report specifying the performance of every aspect of the software. The QA team should be notified of every failed test to ensure quick resolution.

Features of Unit Test

To carry out effective and quality unit testing, it is essential to create good unit tests. But what is a good unit test, and how does it help identify bugs in our software product? Consider these features of an effective, good unit test:

  1. Fast: Large and complex projects require hundreds of unit tests. A good unit test is something that takes very little time to run, i.e., milliseconds. Sometimes you need to run a test repeatedly to check if the specific bug has been eliminated or not. So, if unit tests are slow to process, you might skip those tests.
  2. Easy Debugging: Each unit test should be clear enough to tell a story about the behavioral aspect of the application, making it easy to understand. Some tests execute successfully when run individually but fail when integrated, indicating a design flaw.
  3. Independent and Isolated: Good unit tests are standalone and run in isolation. Also, they are independent of external factors, such as file systems or databases. Make sure that the unit tests you write should not depend on other test cases.
  4. Self-checking: Unit tests should be capable of detecting whether they are passed or failed automatically without any human intervention.
  5. Repeatable: A good unit test should produce the same results each time you execute it.

Advantages of Unit Testing

  • Exposes all possible defects in the software product at early stages
  • Enhances code readability and quality
  • Simplifies documentation and enables code reuse
  • Saves time and money in catching errors quickly that otherwise might move to later project stages
  • Improves deployment speed to speed up project completion and debugging time

Disadvantages of Unit Testing

  • Implementation costs when introducing and implementing new functionalities
  • Hinders prototype development, where the underlying code changes rapidly
  • The tests use the functionality, thus making it harder for the IDEs to see whether the functionality is in use.
  • Tests with interdependencies might impact results when an individual codebase is changed

Different Unit Testing Techniques

  1. White-Box Testing: While-box testing, also known as glass box testing or transparent testing, entails the tester knowing the entire internal functionality of the product. It enables testers to verify the internal working of the software system, i.e., its code, infrastructure, and integration with external systems.
  2. Black-Box Testing: This testing is the opposite of white-box testing, where the tester doesn’t know the internal functionality of a product. Testers in black-box testing, also known as behavioral testing, test the functionality of the software product without knowing its code structure and implementation details.
  3. Gray-Box Testing: Gray-box testing is also known as semi-transparent testing. It is a combination of black-box and white-box testing. In this type of testing, testers have limited knowledge of the internal working of the software product. Subtypes of unit testing in this category include matrix testing, pattern testing, orthogonal pattern testing, and regression testing.

Common Challenges in Unit Testing

Unit testing isn’t always simple. Consider the following challenges throughout the testing journey:

  • Labeling: Test labeling is essential for a smooth testing operation. If you forget this vital task, it could lead to great confusion among team members.
  • Understanding the Entire Code: Developing software requires excessive coding. Getting along with the entire code can be challenging and tedious for the developers, resulting in testing delays.
  • Misunderstanding Test Doubles: This issue occurs when your mocks are more complicated than the production code. In such a scenario, test doubles help in simplifying tests. The major challenge is when the test double has different names in different books.
  • Debugging: This requires significant time and effort. So, if any of the tests fail constantly, the consequent debugging will result in more delays.

Best Practices for Unit Testing

The following are some of the best practices to use in unit testing for better outcomes:

  • Make Sure All Units Are Independent: Any dependencies will impact the unit tests whenever there is a new change requirement. Also, dependencies increase the complexities while debugging test cases.
  • Test Multiple Use Cases: A single unit relates to several use cases; thus, a tester has to test each use case in different test cases, allowing the teams to refactor or change the code effectively.
  • Use AAA (Arrange, Act, and Assert): This pattern will separate what is being tested from the “arrange” steps, reducing the intermixing of the assertions using “Act” and making the test cases more readable.
  • Label Properly and Consistently: Always make sure to have proper naming of the variables, test cases, scenarios, etc., to avoid using magic strings for better readability and understanding among teams.

Best Tools for Unit Testing

A myriad of tools is available to help you conduct unit testing:

1. Jtest


Jtest is an open-source IDE plugin offering one-click actions to create, scale, and maintain unit tests. You can use this tool to automate the critical aspects of Unit Testing to save your time, which allows the team to focus on business logic and create more meaningful test suits.

2. JUnit


JUnit is a free unit testing tool most suitable for Java unit testing. This tool comes with support for the assertions that identify the test method. JUnit first tests the data and then uses the data within the code.

3. NUnit


NUnit is a testing framework that is well-suited for .Net programmers. You can use this open-source tool for writing manual scripts. This tool comes with the support for data-driven tests that can run simultaneously.

4. JMockit


JMockit is an open-source code coverage tool. It uses recording and syntax verification for mocking the API. This tool comes with line, path, and data coverage.



You can use this open-source tool to analyze and report written code in Java, similar to JMockit. EMMA also supports the different types of coverage, such as method, line, basic block, etc.

6. PHPUnit


PHPUnit is well-suited for PHP developers. You can use it to test units individually with the help of the pre-defined assertion methods to make sure that the system behaves in a specific manner.


Unit testing is the most important type of software testing that eliminates all the issues at the early stage of development. It helps us find the root cause of errors and prevents them from migrating to the next level. Since every unit or component of the software product gets checked in unit testing, unit testing assures high-quality software.

Any questions or comments? Feel free to share them in the comments section below.

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Sameeksha Medewar

Sameeksha Medewar

Sameeksha is a freelance content writer for more than half and a year. She has a hunger to explore and learn new things. She possesses a bachelor's degree in Computer Science. View all posts by the Author

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