We live in a time when users expect software to be ready to use whenever they want it, and the microservices model ensures that an application will not be down for maintenance when a user wants to use it.

Most microservices are using application programming interfaces (APIs), which are a set of commands for how a service can be used. And most APIs are using Representational State Transfer (REST) requests through Hypertext Transfer Protocol (HTTP) to request and send data.

In spite of this fact, many software testers continue to automate their testing with user interface (UI)-based tests that interact directly with the browser. This is largely due to the success of the Selenium suite of tools for test automation, which runs in a web browser.

Selenium has been available for several years, and most software testers are familiar with its use. But the most familiar tool is not always the most appropriate tool to use in test automation.

While some UI testing will always be needed to verify that elements appear on a page and can be interacted with, API tests are much faster and more reliable than UI-based tests. When testing things like adding and removing records from a database, automated UI tests can be time-consuming and repetitive. API tests allow for rapid record manipulation.

Furthermore, API testing allows the tester to find bugs earlier in the development process, often before the UI has been created. And API testing allows the tester to make requests that might not be allowed through the UI, which is crucial for exposing potential security flaws in an application.

Because changes in software happen at such a rapid pace today, it’s important to have tests that provide fast feedback for developers and testers. API tests can fill this need. We’ll describe the fundamentals of API testing, including how REST requests work and how to set up requests and assertions.