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In order to learn how to test your APIs, especially how to load test your APIs, let’s first find out some essential info on APIs and RESTful APIs.

What is an API? (Application Programming Interface)

API stands for Application Programming Interface, which is a set of functions that allows two applications to talk to each other. Also, APIs allow interaction between various software components, microservices by exchanging responses between users and systems.

What is RESTful API?

REST stands for Representational state transfer, and is an architecture standard for designing networked applications, interactive applications that use multiple Web Services. More details about REST and RESTful APIs can be found here.

An API is considered RESTful if it ticks all criteria below:

  • A client-server architecture with requests made through HTTP (Hypertext Transfer Protocol).
  • Stateless communication which translates that each request is executed like it’s made from scratch, no information is stored about the client, or about the past transactions.
  • Cacheable data between client and server.
  • Uniform interface which tells that resources should be uniquely identifiable through a single URL to identify and manipulate resources.
  • Layered system which allows for an architecture composed of multiple layers of servers, hierarchies which are invisible to the client.

Overall, REST APIs are simpler to implement comparing to SOAP (Simple Object Access Protocol) APIs, which requires additional requirements when starting a transaction, relies heavily on XML and uses WSDL – Web Service Description language.

REST uses methods GET, PUT, POST, DELETE to link resources to actions within a client-server relationship, its main purpose is to offer simplicity and end-user satisfaction for a wide audience.

Which response formats are used in REST APIs?

REST uses HTML, XML, plain text, and JSON as potential responses, however, the most popular one is JSON (JavaScript object notation) because is easily readable by humans and easily to integrate with other frameworks and tools since it’s widely accepted.

api client server

Now that we have a basic understanding of REST APIs and what a RESTful API stands for, we can continue and have a look at load testing, and what is the purpose of load testing or check what is a good example of load testing, this can apply to your website and APIs as well.

We can follow the steps to start API load testing by following some of the previous posts that include load testing scenarios, performance testing vs. load testing, and an example of APIs to be tested in the cloud.

Written by Bogdan Vazzolla.

LoadFocus is a cloud testing platform, a load and stress testing tool which provides the infrastructure to run tests with thousands of concurrent users, from multiple cloud locations, in less than a few minutes, keep history of the results, compare different runs to inspect performance improvements or performance degradation. It also supports running JMeter load tests from the cloud and monitoring and audit web and mobile performance.

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