Unit Testing

Unit Testing chart

Termed as an extremely complex and expansive process, software testing involves testing of heterogeneous components and elements, of varying size, scope, and form. From the minutest element of the software to the most composite one, this process is capable of verifying and validating the quality, reliability, performance, effectiveness, etc., of the software. Unit Testing, which is a type software testing technique, is used by the team of software testers to validate the accuracy of the smallest component of the software, the UNIT.

Let’s understand more about this type of testing, with the aid of the following discussion:

What is meant by Unit Testing?

Considered to be the first level of software testing life cycle (STLC), unit testing is performed prior to the execution of integration tests. The objective of this testing is to validate the correctness and completeness of the smallest component of the software- Unit, which is the smallest testable part of the software that is capable of accepting and producing input and output, respectively. These units are integrated, to form the modules or the system.

Performed by a selected group of software developers, uni testing involves evaluation of each unit, before it is integrated to for the system. These units are verified and validated on the basis of specified requirements, by testing them in isolation to identify, analyze and fix defects.

Unit Testing chart

Why Unit Testing is Necessary?

It is an effective testing, which may prove to be economical for the software development process, as detecting the defects in the integrated system is much more complicated, whereas it is easier to find the bugs & defects in the smaller units. Early detection of the bugs in the software development process enables the developer to fix them at the initial stage of the development process, thereby saving both time & cost of the project.

Moreover, with the assistance of this testing technique, the team of developers can tackle various issues related to the software product, as it is focused on:

  • Handling errors and defects.
  • Ensuring the functional correctness and completeness of the software product.
  • Checking input values and correcting output data.
  • Optimizing algorithm and performance.
  • Identifying, analyzing, and rectifying defects.

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Features of Unit Testing:

With its objective to test each unit of the software product independently, the process of unit testing is executed during the initial stage of software testing. It is an integral part of computer programming and it is used to evaluate the individual units of the source code of the product. Other features of this testing technique are:

  • Performed before integration testing, unit testing is also known as component testing.
  • It is a component of test-driven development.
  • Forms the foundation of extreme programming, as it excessively relies on automated unit test frameworks.
  • Evaluates individual units of the software product.
  • Software developers write the test and run the test for unit testing, to validate the compliance of the software code with its design as well as to ensure its intended function.
  • It may include testing techniques like walk-through, review & inspection of programming code.
  • It also demands strict possible test plans for each isolated units, to produce effective results.
  • Automated testing is preferred for this type of testing. However, manual testing may also be used for this type of testing.
  • Requires plenty of time & patience to focus & perform testing on each unit.
  • Provides an effective approach to trace & resolve the errors in the programming code at an earlier stage.
  • Saves time & cost of finding & resolving the error, at later complex stage.

How to do Unit Testing?

Though the unit testing process is generally performed by the software developers or their peers, it some rare cases it can also be executed by the team of testers. Whether performed manually or through automated tools, it follows a set process, which usually consist of the following activities:

  • Defining and creating Unit Test Plans.
  • Based on the specified test plans, unit test cases are designed and prepared.
  • Execution of these test cases on individual units.
  • Fix the bugs (if any found) and re-evaluate the unit.
  • The cycle of testing keeps on repeating, until the unit gets rid of all the bugs.

Types of Unit Testing:

There are basically three types of unit testing, which can help the team of unit testers in testing each unit of the source code in isolation. Each of these types of unit testing cater to different requirements of the software and ensures its proper functioning. The types of unit testing are:

  1. Black Box Testing: This type of unit testing enables the team to test the user interface of the software, along with its input and output.
  2. White Box Testing: White box testing is another important type of unit testing, which is used by the developers to test the functional behavior of the software product and to validate their execution.
  3. Gray Box Testing: Finally, the third type of unit testing, gray box testing is used to execute test suite and test cases, perform risk assessment, and to test various test methods.

Unit Testing Techniques:

The process of unit testing can be executed with the assistance of three important testing techniques, which are:

  1. Structural Technique: A white box testing technique, structural technique uses the knowledge of the software system’s structure and internal implementation to design and create test cases. The testers during this testing should have in-depth knowledge of the code for test execution, hence it is performed by the team of developers, with the assistance of the following methods:
  2. Functional Testing Technique: Performed to validate the functionality of the software product as well as to ensure it behaves in the intended manner, functionality testing is executed by the team. It is a black box testing technique that involves:
    • Input domain testing.
    • Boundary Value.
    • Syntax Checking.
    • Equivalence Partitioning.
  3. Error Based Techniques: Issues in a code can be best tracked by the individual who designed it. For this, error based techniques are used, which allow the team to identify defects, bugs, and other discrepancies in the software. It involves:

Unit Testing Importance in Extreme Programming:

As mentioned above, the importance of unit testing in extreme programming is immense and it acts as its foundation or base on which it is highly dependent. In extreme programming (XP), unit testing extensively uses testing frameworks. Moreover, these unit test frameworks are utilized by here in for the creation of automated unit tests, which are further used to create unit tests for test driven development. Other benefits of unit testing in extreme programming are:

  • It allows rapid and convenient integration.
  • Here, tests are written before the test code.
  • The tests is highly dependent on testing frameworks.
  • Enables the team to test all classes in the application at any time.
  • Promotes simpler and more confident code development and refactoring.
  • The unit tests in extreme programming are also used as regression testing.
  • Simplifies code integration and enables accurate documentation.

Challenges in Unit Testing:

While executing the process of unit testing, the team can encounter various issues and challenges, which can hinder the smooth testing and inhibit the team from getting expected results. Some of these challenges witnessed by the testers are:

  1. Uncertainties or Trouble With Test Names: Names that don’t reflect the intent of the testing or miscommunicate the the test type can increase the challenge of testing for the team. Moreover, it can increase confusion among team members, which can further impact the testing of the software.
  2. Understanding the Entire Code: Software development requires excessive amount of coding and understanding the entire code can be extremely difficult and tedious for the developers. Moreover, it can delay the process of testing and product release.
  3. Problems With the Test Doubles: If the mock codes require more testing than the production code, then it is an indicator that there is an issue in the product, as the aim of these mock objects is to simplify the process of testing.
  4. Finding Dependencies: Finding dependencies in the software product can be a hassle free task, which can hinder the process of testing.
  5. Frequent debugging of Tests: Debugging is a complex task that requires great efforts and time. Hence, if the tests fail constantly and often require testing and debugging, it can increase the challenges in testing the software.

Unit Testing Advantages and Disadvantages:

One can gather proper understanding of a process by getting an insight into its advantages and disadvantages. Ergo, to help you get a better understanding of unit testing, here are some of its advantages and disadvantages

Advantages of Unit Testing:

  • It eliminates the dependencies on other modules.
  • Allows testing of individual parts of the software.
  • Validates the quality and accuracy of the program code.
  • Team can execute unit testing before the culmination of the development process.
  • In unit testing the code is modular, which makes them more reusable.
  • Due to its modular nature, the team can test a part of the project, without waiting for the others to be complete.
  • Reduces the cost of testing, as defects are identified and fixed in the early stages of development.
  • It facilitates change, simplifies documentation, as well as integration.
  • Increases the reliability of the code.
  • Simplifies the debugging process.

Disadvantages of Unit Testing:

  • Unit testing cannot be used for a comprehensive detection of errors in the program.
  • It is impossible for the team to analyze and evaluate every execution path in the software.
  • As the focus of unit testing on evaluating smallest component of the software, it does not perform integration testing.
  • There can be difference in platform, as the product is not developed and tested on the platform where it will be deployed.
  • It requires for the team to maintain rigorous discipline throughout the process to ensure the compliance of actual and expected results.

Unit Testing Frameworks and Tools:

One of biggest advantage of unit testing is that it often executed with the assistance of testing tools and frameworks, which increase its effectivity as well as efficiency. From making the process agile and robust, to helping the team get accurate results, the benefits of using unit testing tools are several. Since tools are an essential part of unit testing, it is important for us to list some of the most popular unit testing tools, available in the IT industry.

Hence, the popular unit testing tools are:

  1. JUnit.
  2. NUnit.
  3. JMockit.
  4. REST Assured.
  5. Selenium.
  6. EMMA.
  7. Quilt HTTP.
  8. Spock Framework.
  9. Cucumber.
  10. DBUnit.
  11. HTMLUnit.
  12. PHPUnit.
  13. SimpleTest.

Get the detailed information of unit testing frameworks here.

Important Things to Consider in Unit Testing:

While performing unit testing, there are multifarious aspects that need proper consideration and monitoring to validate the quality, effectiveness, as well as the accuracy of testing. Ergo, here are some important things to consider while executing uni testing:

  • Unit testing should be performed independently, to ensure that any modifications and changes implemented in the software requirements are not affecting the unit test cases.
  • The process of test execution should be concentrated on one code at a time.
  • The bugs and defects, detected by the team during the testing process, should be resolved and fixed before the commencement of the next phase of software testing life cycle (STLC).
  • Test cases should be comprehensive and understandable.
  • The testing environment should be isolated from the development environment in unit testing.
  • Find an appropriate and effective tool for the process of testing.
  • Perform rigorous and frequent unit tests.

Still unsure about what to test, well follow our unit testing checklist and drive away your testing related apprehensions.

Unit Testing Infographics:

unit testing Infographics


From software’s functionality, performance, stability, reliability, to its compliance with privacy policy, standards, and more, there are numerous aspect of a software product that are ensured through testing. Likewise, unit testing also plays an integral part in validating the quality and effectiveness of the software. It ensures the products code and functionality, and makes the software reliable and efficient. Hence, it is vital for the team to execute unit testing during the early stages of software development life cycle (SDLC).Also, find a detailed comparison between Unit Testing and API Testing and enhance your knowledge efficiently.

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