Integration testing is a software testing method used to verify whether different software components or systems interact with each other as expected. It is often conducted after unit testing and before system testing. Integration testing verifies the correctness, completeness, and quality of the combined parts of an application.
It aims at catching possible issues when different components of a software system are combined. This step is highly important as potential problems might arise when integrating multiple components of an application. It is also necessary to assure that the individual components, which are assumed to work correctly per their own tests, also continue to work correctly when joined together.
Integration testing is typically divided into two categories; incremental (also called bottom-up) integration testing and big-bang (otherwise known as top-down) integration testing. Incremental integration testing starts by testing the bottom two layers, where the lower layers are tested first and combines more and more layers until the complete system is tested. Whereas, big-bang integration testing combines the software layers top down in order, and tests the entire system as soon as the layers are integrated together.
Integration testing is also known as interface testing. In order to ensure that interfaces between internal modules and between internal and external modules are functioning as expected, software testers validate the interfaces to prove the correctness, completeness, security, reliability and testability of the system.
It should be noted that integration testing is a time-consuming process that requires a lot of resources. For software teams, it is important to ensure that integration testing is effective in order to improve the quality of the system quickly and efficiently.
