APIs have become the center of software development, connecting and transferring data and logic across disparate systems and applications. Luckily, testing them can greatly improve the efficiency of your testing strategy as a whole, helping you deliver software faster than ever.
What is API Testing?
API testing involves testing the application programming interfaces (APIs) directly and as part of integration testing to determine if they meet expectations for functionality, reliability, performance, and security. Since APIs lack a GUI, API testing is performed at the message layer. API testing is critical for automating testing because APIs now serve as the primary interface to application logic and because GUI tests are difficult to maintain with the short release cycles and frequent changes commonly used with Agile software development and DevOps.
When you release a new version of the system (e.g. changing some of the business components or internal data structures) you need to have a fast, easy to run set of API regression tests that verify that those internal changes did not break the API interfaces and therefore the client applications that rely on the APIs will continue to function as before.
Why is API Testing Important Now?
The move to cloud computing has highlighted the importance of Application Programming Interfaces (APIs). With the rise in cloud applications and interconnect platforms, API testing is a necessity. Many of the services that we use every day rely on hundreds of different interconnected APIs, if any one of them fails then the service will not work.
API Testing Approach
Testing for APIs is similar to testing any other software, except that you need to think a bit more technically. Unlike GUI based systems, there are no text fields or buttons which you can test, you have to essentially hit the backend calls that are made when a user would perform an action. Since APIs help systems to integrate and communicate, it is important that you check each system endpoint where an API call can make impact.
In order to effectively test an API, the tester should first determine the functional scope of the API. Next the test environment should be set up with proper configuration of servers, databases and every resource the API interacts with.
Web Service Testing
A Web service is a unit of managed code that can be remotely invoked using HTTP, that is, it can be activated using HTTP requests. So, Web Services allows you to expose the functionality of your existing code over the network. Once it is exposed on the network, other application can use the functionality of your program.
There are two broad classes of web service:
• Simple Object Access Protocol (SOAP)
• Representational State Transfer (REST)