Difference Between Unit Testing and Integration Testing

Difference Between Unit Testing and Integration Testing: If you’re writing code, you might have heard of unit testing and integration testing. I’m going to explain what they are and show why it’s worth your time to go out of your way to do these tests.

I’d also like to stress that there is a difference between unit testing and integration testing. Integration tests will fail if your code calls the wrong methods, but they aren’t going to tell you if you have good data/control flow. Unit tests will let you know that your data is incorrect, however, they won’t be able to tell you which part of your code must be fixed (it just means that the calculation was erroneous). Think of unit testing as an extra check to make sure your data is correct, whereas integration testing will help you find the actual components wrong in your code.

Unit Testing

Unit testing is a way of writing code that will test one specific component of your app against certain criteria. In other words, it tests something very small. A perfect unit test will be able to tell you if one of your methods fails, but it won’t tell you why the method failed. It’s important to note that a series of unit tests reviewing a small component of code together is called an integration test (see “Integration Testing” section).

Integration Testing

Integration testing is different than unit testing because it’s not going to be as granular. An integration test might do some setup for you, run through a bunch of steps, and then make sure that it did what it was supposed to. It doesn’t do a step-by-step like unit testing but rather checks your system as a whole.

Integration tests are going to help you find bugs with your data flow because they’re checking the way your app works on a more granular level. Unit tests are going to help you catch bugs in your data.

Difference Between Unit Testing and Integration Testing

Both unit and integration testing serve as an important part of the software development process. But unit testing is mainly used to write simple tests for each of the smaller components within an application. As a developer, I have found that writing these unit tests helps in identifying areas with weak code or when you are not using the best design patterns.

Integration testing can be very useful in scaling up your application development as it saves you from rewriting all the tests every time something changes within another module.

Both unit and integration tests play a vital role in software development but it is important to identify which parts of your code require which form of testing.

Here are some of the key differences:

Unit Testing

  • Unit Testing is done at the class level(Method or functions).
  • Unit Testing can test private functions in a class.
  • There are no dependencies needed with Unit Testing.
  • There can be total isolation in Unit Testing.
  • It’s more granular.
  • It’s better for new code.
  • Best Way to refactor legacy code.
  • Unit Tests can be run against a build(local or remote).

Integration testing

  • Integration Testing is done at the module level(class or methods).
  • Integrations Tests are more granular then Unit tests.
  • Dependency injection can be used for Integration testing.
  • Test dependencies can help with Integration Testing.
  • Isolation is not always possible with Integration Testing.
  • Integration tests are less granular when compared to Unit Tests.
  • Testing Services and DAO’s is better done with Integration testing.
  • Integration Testing can’t be run against a build.(local or remote).


If you have new code, then write unit tests. If you have old code but want to make sure your data is correct and it’s flowing correctly through the system, write integration tests.

I hope this article was helpful in explaining a few things about testing! I’d love to hear your thoughts or questions in the comments below!

I love open-source technologies and am very passionate about software development. I like to share my knowledge with others, especially on technology that's why I have given all the examples as simple as possible to understand for beginners. All the code posted on my blog is developed, compiled, and tested in my development environment. If you find any mistakes or bugs, Please drop an email to softwaretestingo.com@gmail.com, or You can join me on Linkedin.

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