Unit Test vs Integration Test – Difference Between Them

Key Difference between Unit testing vs Integration testing

Unit testing is a testing method by which individual units of source code are tested to determine if they are ready to use, whereas Integration testing checks integration between software modules.
Unit Testing test each part of the program and shows that the individual parts are correct, whereas Integration Testing combines different modules in the application and test as a group to see they are working fine.
Unit Testing starts with the module specification, while Integration Testing starts with interface specification.
Unit Testing can be performed at any time, on the other hand, Integration Testing is performed after unit testing and before system testing.
Unit Testing is executed by the developer, whereas Integration Testing is performed by the testing team.
Unit Testing errors can be found easily, whereas in Integration Testing, it is difficult to find errors.
Unit Testing is a kind of white box testing, whereas Integration Testing is a kind of black-box testing.

What is the Unit Test?

Unit Tests are conducted by developers and test the unit of code( aka module, component) he or she developed. It is a testing method by which individual units of source code are tested to determine if they are ready to use. It helps to reduce the cost of bug fixes since the bugs are identified during the early phases of the development lifecycle.

What is Integration Test?

Integration testing is executed by testers and tests integration between software modules. It is a software testing technique where individual units of a program are combined and tested as a group. Test stubs and test drivers are used to assist in Integration Testing. Integration test is performed in two way, they are a bottom-up method and the top-down method.

Difference Between Unit Test and Integration Test

Below is a detailed comparison between Unit testing vs integration testing

Unit test	Integration test
The idea behind Unit Testing is to test each part of the program and show that the individual parts are correct.	The idea behind Integration Testing is to combine modules in the application and test as a group to see that they are working fine
It is kind of White Box Testing	It is kind of Black Box Testing
It can be performed at any time	It usually carried out after Unit Testing and before System Testing
Unit Testing tests only the functionality of the units themselves and may not catch integration errors, or other system-wide issues	Integrating testing may detect errors when modules are integrated to build the overall system
It starts with the module specification	It starts with the interface specification
It pays attention to the behavior of single modules	It pays attention to integration among modules
Unit test does not verify whether your code works with external dependencies correctly.	Integration tests verify that your code works with external dependencies correctly.
It is usually executed by the developer	It is usually executed by a test team
Finding errors is easy	Finding errors is difficult
Maintenance of unit test is cheap	Maintenance of integration test is expensive