Difference between Unit Testing and Integration Testing

Differences Automation Testing Testing Tools

Testing is the most important stage in the process of delivery of any software product, as it not only validates the quality of the product but also provides an opportunity to the developer to improve it further.

Unit testing and integration testing are both software testing techniques, but they are quite different from each other in their scope and they focus on different parts of the software.

Read this article to learn more about unit testing and integration testing and how they are different from each other.

What is Unit Testing?

Unit testing is a type of testing technique in which a single module is tested at a time. It is also known as white box testing. Unit testing checks if a small piece of code in the application is doing what it is supposed to do. In unit testing, a single module is going to be tested at a time, hence the focus of the tester is on the internal design of the application as well.

Unit testing is performed as the first stage of testing and it is generally performed by developers of the application. Parallel testing is not supported in unit testing because a single module is tested at a time in unit testing.

As a single module is tested at a time, so defects get easily identified and are locked as per module. Unit testing generally does not depend on the size of project, so it can be performed in both small and large sized projects.

What is Integration Testing?

Integration testing is a type of testing in which multiple modules are tested to verify if different pieces of the modules are working together as expected. Thus, integration testing helps to validate the collection and interface modules of the product.

Integration testing is generally performed after performing the unit testing, because this testing requires the knowledge of interlinked modules and their interactions. Importance is given to the functionalities in the system interface among individual modules.

Integration testing covers only the functional testing of the product. It is often performed by test engineers and developers.

Difference between Unit Testing and Integration Testing

The following are the important differences between Unit Testing and Integration Testing −

Key	Unit Testing	Integration Testing
Definition	Unit testing is the testing where primarily single module is tested or it checks if the small piece of code is doing what it is supposed to do.	Integration testing is the testing where multiple modules are tested to verify that if different pieces of the modules are working together as per expectation or not.
Focus Area	A single module is going to be tested at a time, so the focus of the tester is on internal design of the application as well.	Multiple modules get integrated and are tested as a single module so tester focus more on integrated functionality rather on internal design of the application.
Perform stage	Unit testing is performed at the first stage of testing as it is performed first of all other testing processes.	Integration testing is performed after all modules get integrated are done with unit tested i.e. Integration testing is done after unit testing and before System testing.
Abbreviation	Unit testing is also known as white box testing.	Integration testing is known as black box testing.
Tester	As unit testing as mentioned in above points performed at first stage of testing so generally performed by developers.	Integration testing is done after all modules get integrated and thus performed by Testers.
Defect Detection	In unit testing, the detection of defects is comparatively easy as single module interaction at a time.	While in case of Integration testing, detection of defects is comparatively difficult as compare to Unit testing.

Conclusion

The most significant difference that you should note here is that, in unit testing, only a single module is checked at a time; whereas in integration testing, multiple modules are tested simultaneously.