https://softwaretestingboard.com/unit-test-vs-integration-test/
Unit Test
When you want to test just a small component or part of a complete design product at a time then that test is called Unit Test. It’s important to understand that unit tests do not test any other code that your application may contain – they only test the smallest pieces of code within your application.
Integration Test
Integration tests are designed to test how your application works when it interacts with another application – be that in an automated fashion or via manual manipulation. These tests usually require an entire deployment of your application (or even multiple deployments) where you can manually interact with it. Integration tests are more complex than unit tests because they often require access to external services and databases, which makes them harder to automate.
Key Differences Between Unit Test and Integration Test
Unit test is the testing of individual units, while Integration test is the testing of the entire application. The unit tests are mostly used to check whether the app functionalities are working as intended or not.
The main difference between unit and integration tests is that integration tests run against an entire application, not just a single component. Integration tests must be thorough for them to be effective.
Unit tests are used to test the behavior of a single unit and Integration tests for the behavior of a system.
The unit test alone is not enough to test your code. You need integration tests as well. An integration test verifies that both the front-end and back-end work together as expected. When I say “both”, I mean the front-end and back-end don’t interact with each other in unexpected ways.
Integration tests are usually very small and quick to execute, whereas unit tests tend to be larger and take longer to execute. For example, if you have a class that has multiple functions that need to be tested, it may be easier and quicker to write an integration test for those functions rather than writing many individual unit tests for each function individually.
Another major difference between unit tests and integration tests is the frequency with which these tests are carried out. Carrying out a unit test is much easier in comparison to the integration test because the latter depends on both external and internal dependencies or in other terms – real dependencies.
Also, if you have conducted the integration tests once then you must maintain them properly because anything from the previously performed test can interfere with and disrupt the current analysis and its results.
Bottom line
If you want your software application to be successful, you can’t launch it without having it tested for both unit tests and interaction tests. Every test has its pros and cons and similarly, they can find out some weaknesses that are missed in other tests. So I think it is safe to say that in this case of the Unit test vs Integration test, both the tests are necessary and both of them complement each other.
Source https://softwaretestingboard.com/unit-test-vs-integration-test/
