Consumer orientation has changed the structure of software. Modern applications are scattered across mobile devices and web browsers, so users can access services anytime and anywhere. In addition, applications are no longer self-contained. They are made up of multiple service components that are linked at runtime. How does an application programming interface, or API, affect the interaction with the end user? And why is API testing becoming a normal practice for IT companies that provide quality assurance services? Let's try to figure it out.
What API is
API is a set of tools, using which one program can exchange data with another. This approach facilitates communication between modules, applications, and back-end systems. API testing helps specialists to promptly know when something goes down and fix the problem before users notice any inconsistency.
Simplistically, the performance of an API can be compared with taking an order in a cafe. A visitor selects a dish from a menu and sends their request to the kitchen via a server. The server, in turn, gives the task to the chefs and returns to the visitor with a plate of cooked food. Here, the server acts as an API, connecting one program (the visitor) to another (the kitchen).
A typical application has three distinct layers: the presentation (or user interface - UI) layer, the business layer, and the database layer for modeling and managing data. As you can see in the picture below, an API focuses on business logic.