What is the Difference Between Unit Testing and Integration Testing

The main difference between unit testing and integration testing is that the unit testing checks whether the individual modules work as expected while the integration testing checks a combination of individual modules to see whether they work properly as a group.

Software testing is an important phase in software development. It helps to find out whether the software meets the business requirements. Moreover, software testing helps to reduce bugs and provides a working product to the end customer. Also, there are various levels of testing. And, two of them are unit testing and integration testing.

Key Areas Covered

1. What is Unit Testing
      – Definition, Functionality
2. What is Integration Testing
     – Definition, Functionality
3. What is the Difference Between Unit Testing and Integration Testing
     – Comparison of Key Differences

Key Terms

Integration Testing, Unit Testing

What is Unit Testing

Unit testing is the type of testing that checks whether individual modules work properly. It helps to check the functional correctness of standalone modules. The primary objective of the unit testing is to identify, analyze, and fix the defects in each unit by isolating it from he system.

For example, assume a banking application. First, the user should log in to the system by entering the username and password. The login is a module in the system. Some unit test cases to perform unit testing on the login module are as follows.

Check response for valid username and password.

Check response for invalid username and password.

Check response when username and password are empty.

Usually, developers perform unit testing. They can use software such as JUnit to perform unit testing.

What is Integration Testing

Integration testing is a type of testing that combines individual modules and test them as a group. It checks the data transferring between multiple modules. For instance, assume a banking application. The user checks the current balance module. It shows 2000. Then, he visits the transfer module and transfers 1000 to a third party. Once again, he checks the current balance. Integration testing checks the data transferring between these two individual modules (current balance, transfer module) to see whether they work properly as a group.

If the current balance module is ready, but the transfer module is not, then the software tester can create a stub for the transfer module. It is not a complete implementation of the transfer module, but it sends data between modules to carry on testing. Similarly, if the transfer module is ready, but the current balance module is not ready, then the software tester can create a driver instead of the current balance module. It is not a complete implementation of the current balance module, but it sends data between modules to carry on testing.

There are mainly two approaches to integration testing. They are as follows.

Top-down approach – Test the higher level modules first. It can require creating stubs.

Bottom-up approach – Test the lower level modules first. It can require creating drivers.

Difference Between Unit Testing and Integration Testing

Definition

Unit testing is a level of software testing where individual units of a software are tested. In contrast, integration testing is a level of software testing where individual units are combined and tested as a group. This is the main difference between unit testing and integration testing.

Functionality

Another difference between unit testing and integration testing is that unit testing checks the functionality of modules or units while integration testing checks the data transferring among multiple modules or units.

Performed By

Developers perform unit testing while software testers perform integration testing.

Conclusion

Unit testing and integration testing are two levels of testing. The main difference between unit testing and integration testing is that the unit testing checks whether the individual modules works as expected while the integration testing checks a combination of individual modules to see whether they work properly as a group.

Reference:

1. “Levels of Software Testing”, TutorialRide.com, Available here.

Image Courtesy:

1. “762486” (CC0) via Pixabay