What is Unit Testing?

Software testing is an essential procedure for developing quality software and it also ensures that you do not launch the software to the end-user without testing it. There are different types of software testing each kind of testing is specific uses, benefits, and limitations.

e.g.: Integration testing, System testing, Unit testing, Functional testing, etc.

Unit testing is software testing where you test every line of code in the program. It is also called white-box testing or structural testing Glass box testing or transparent testing or open box testing etc.

What is Unit Testing?

Unit testing is the type of software testing where individual units of software or components of a software are tested. Its main purpose is to prove that each unit of software code performs as expected. It is done by the developer during the development (coding phase) of an application. Unit testing isolates a section of code and verifies its correctness. An entity can be an individual function, method, procedure, module, or object.

In the SDLC, STLC, v model, unit testing is the first level of testing done before integration testing. It is a white box testing technique usually performed by the developer. However, in the practical world, QA Engineers also do unit testing due to time constraints or developers’ reluctance to test.

Types of Unit Testing

There are two types of testing in unit testing.

  1. Manual testing
  2. Automation testing

1) Manual Testing

Manual testing of code requires the developer to manually debug each line of code and test it for accuracy. This may require a step-by-step instruction set as well if the functionality is complex.

2) Automation Testing

In automation testing, the developer tests the code. This is typically facilitated through unit testing frameworks that are not deployed to production. Other times, a developer may choose to write test code without the structure and manually comment it out before deployment.

In most cases manual checks take time. But for some cases, when it is not possible to write automated test cases to cover each scenario, the manual is often the preferred method.

qa automation testing services

How to do Unit Testing?

First of all, developers write the code to test some specific function in the application. Developers also isolate this function to test more deliberately which reveals unnecessary dependency between the function being tested and other units so dependency can be eliminated. Developers generally used a unit test framework to develop automated test cases for unit testing.

Advantages and disadvantages of unit testing


  • The main advantage of 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 API.
  • It enables testing parts of the project without waiting for others to be completed.
  • It allows the programmer to redefine the code.
  • It is an important practice in the software development process to detect defects in the software in the early stage of development to save time and cost.
  • The advantages of unit testing are it reduces bugs, increases developer productivity, and encourages modular programming.


  • To write unit test cases this process is time-consuming.
  • Unit testing does not cover all the errors in the application/module because these chances are their errors in the module/application while doing integration testing.
  • It is consuming more time for maintenance when the source code is changed frequently.
  • It is not cover non-functional testing parameters such as scalability the performance of the system etc.
  • It is not efficient for checking errors in the UI part of the system.


Unit Testing is the foundation task in any software testing process. Formerly it was a manual task performed by the developers or test engineer but with the changing need, each and every task performed by the Software Development Process has similarly become automated, unit testing also became an automatic task with using the tools.

make your app bug free

Finally, this test is only necessary to test each function independently. This type of testing saves time and cost if the same is issued at acceptance testing then, in that case, the price will be more as compared to the unit testing. For some time to do testing, there is a requirement to create a mock object to satisfy or fulfill the dependencies of a method or a function. If a function is dependent on other functions and other functions are still not created, then the mock function object is used.


Suraj Prakash

Suraj Prakash working as a junior quality analyst at QACraft. He completed engineering in 2019. In his spare time, he enjoys playing cricket and reading books.