As you develop software in an agile environment, you will come across the need to integrate multiple systems to achieve desired functionality. Upon integrating different systems, it is important to test the functionality of the entire system as well. This is where integration testing comes into play. You will be testing all the integrated systems as a group.
For example, assume that you are going to integrate a Point of Sale system with a CRM to store customer information. You can do the integration via an API. After you create the link, you should do integration testing and see whether the integration is successful or not. This will help you to ensure the overall functionality of your system.
There are multiple approaches to do integration testing. If you have a small system, you may try big bang testing approach. This is where you integrate all modules and proceed with testing the entire unit. If the system is large, you can try incremental testing. This is where you integrate two or more modules at a time and proceed with integration. Likewise, you may also try stubs and drivers testing approach. This is where you use dummy programs for integration and proceed with testing. Another approach for testing is bottom-up testing. This is where you will test the integration of lower modules at the beginning, and then continue to test higher level modules. The opposite of it would be top-down testing, where you test higher level modules first.
No matter how you do integration testing, it is important to determine the best test strategy. Based on that, you can create your test cases. If you have a good understanding about the architecture of the system, you can get a helping hand to proceed with integration testing. You should never ignore the importance of test data, as you do integration testing.
— Slimane Zouggari