Web services and APIs make up a huge chunk of the code in the applications we test, but either we’re not aware of the APIs or we’re asked to focus on the user interface instead. But those APIs are where all of the business logic for the application is exposed, and can hide some pretty nasty bugs. Web services and APIs can be tested in isolation, but they can also be tested in combination with the UI. Understanding how the UI and API work together can make it easier to troubleshoot when things go wrong from the UI. Having this understanding can also create a more complete picture of the application under test.
Sr. Quality Engineer