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Unit Testing – Software Testing

Last Updated : 23 Apr, 2024
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Unit testing is a type of software testing that focuses on individual units or components of a software system. The purpose of unit testing is to validate that each unit of the software works as intended and meets the requirements. Developers typically perform unit testing, and it is performed early in the development process before the code is integrated and tested as a whole system.

Unit tests are automated and are run each time the code is changed to ensure that new code does not break existing functionality. Unit tests are designed to validate the smallest possible unit of code, such as a function or a method, and test it in isolation from the rest of the system. This allows developers to quickly identify and fix any issues early in the development process, improving the overall quality of the software and reducing the time required for later testing.

Prerequisite of Unit Testing

Types of Software Testing 

  • Unit Testing is a software testing technique using which individual units of software i.e. group of computer program modules, usage procedures, and operating procedures are tested to determine whether they are suitable for use or not.
  • It is a testing method using which every independent module is tested to determine if there is an issue by the developer himself. It is correlated with the functional correctness of the independent modules.
  • Unit Testing is defined as a type of software testing where individual components of a software are tested. Unit Testing of the software product is carried out during the development of an application.
  • An individual component may be either an individual function or a procedure. The developer typically performs Unit Testing. In SDLC or V Model, Unit testing is the first level of testing done before integration testing.
  • Unit testing is a type of testing technique that is usually performed by developers. Although due to the reluctance of developers to test, quality assurance engineers also do unit testing. 

Objective of Unit Testing

The objective of Unit Testing is:

  • To isolate a section of code.
  • To verify the correctness of the code.
  • To test every function and procedure.
  • To fix bugs early in the development cycle and to save costs.
  • To help the developers understand the code base and enable them to make changes quickly.
  • To help with code reuse.


Types of Unit Testing 

There are 2 types of Unit Testing:

  1. Manual Testing
  2. Automation Testing

Workflow of Unit Testing


Workflow of Unit Testing

Unit Testing Techniques

 There are 3 types of Unit Testing Techniques. They are

  1. Black Box Testing: This testing technique is used in covering the unit tests for input, user interface, and output parts.
  2. White Box Testing: This technique is used in testing the functional behavior of the system by giving the input and checking the functionality output including the internal design structure and code of the modules.
  3. Gray Box Testing: This technique is used in executing the relevant test cases, test methods, and test functions, and analyzing the code performance for the modules.

Unit Testing Tools

Here are some commonly used Unit Testing tools

  1. Jtest 
  2. Junit 
  3. NUnit 
  4. EMMA
  5. PHPUnit 

Advantages of Unit Testing

  1. Unit Testing allows developers to learn what functionality is provided by a unit and how to use it to gain a basic understanding of the unit API.
  2. Unit testing allows the programmer to refine code and make sure the module works properly.
  3. Unit testing enables testing parts of the project without waiting for others to be completed.
  4. Early Detection of Issues: Unit testing allows developers to detect and fix issues early in the development process before they become larger and more difficult to fix.
  5. Improved Code Quality: Unit testing helps to ensure that each unit of code works as intended and meets the requirements, improving the overall quality of the software.
  6. Increased Confidence: Unit testing provides developers with confidence in their code, as they can validate that each unit of the software is functioning as expected.
  7. Faster Development: Unit testing enables developers to work faster and more efficiently, as they can validate changes to the code without having to wait for the full system to be tested.
  8. Better Documentation: Unit testing provides clear and concise documentation of the code and its behavior, making it easier for other developers to understand and maintain the software.
  9. Facilitation of Refactoring: Unit testing enables developers to safely make changes to the code, as they can validate that their changes do not break existing functionality.
  10. Reduced Time and Cost: Unit testing can reduce the time and cost required for later testing, as it helps to identify and fix issues early in the development process.

Disadvantages of Unit Testing

  1. The process is time-consuming for writing the unit test cases.
  2. Unit Testing will not cover all the errors in the module because there is a chance of having errors in the modules while doing integration testing.
  3. Unit Testing is not efficient for checking the errors in the UI(User Interface) part of the module.
  4. It requires more time for maintenance when the source code is changed frequently.
  5. It cannot cover the non-functional testing parameters such as scalability, the performance of the system, etc.
  6. Time and Effort: Unit testing requires a significant investment of time and effort to create and maintain the test cases, especially for complex systems.
  7. Dependence on Developers: The success of unit testing depends on the developers, who must write clear, concise, and comprehensive test cases to validate the code.
  8. Difficulty in Testing Complex Units: Unit testing can be challenging when dealing with complex units, as it can be difficult to isolate and test individual units in isolation from the rest of the system.
  9. Difficulty in Testing Interactions: Unit testing may not be sufficient for testing interactions between units, as it only focuses on individual units.
  10. Difficulty in Testing User Interfaces: Unit testing may not be suitable for testing user interfaces, as it typically focuses on the functionality of individual units.
  11. Over-reliance on Automation: Over-reliance on automated unit tests can lead to a false sense of security, as automated tests may not uncover all possible issues or bugs.
  12. Maintenance Overhead: Unit testing requires ongoing maintenance and updates, as the code and test cases must be kept up-to-date with changes to the software.

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