Ultimate API Testing Guide for Automation Success

I believe automation engineers are living in a time of great change and API testing is a must for any serious automation testing strategy.

Testers need to stop focusing all their efforts on brittle hard to maintain UI automation tests.

Agile and Continuous Testing (CI/CD) has disrupted standard test automation practices, causing test engineers to rethink how automation is done.

APIs and API testing are needed if you want to succeed with any test automation efforts.

I wrote this way back in 2014 but it still holds true today.

This is a long updated guide, so here’s an overview of what we’re going to cover:

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In a previous post, I’ve covered how No longer is the GUI king.

Today’s automation engineer needs to burrow deeper underneath the GUI to the API level.

There are many reasons why API testing is important:

• More test coverage
• Speed of execution
• Continuous Integration and delivery need fast feedback
• Internet of Things (iOT)

Before we get into API testing tools and techniques let take a quick look at what is an API?

What is API testing?

Application Programming Interface (API) is a specification that acts as an interface for software components. While most functional testing involves testing a user interface like a web page or a .NET form, API testing involves bypassing a user interface and communicating directly with an application by making calls to its APIs.

API testing allows the user to test headless technologies like JMS, HTTP Databases, and Web Services.

For example, many modern web applications business logic lives in a backend API.

When interacting with the frontend, calls are being made to these backed microservices.

So APIs allow different parts of your application to talk to each other.

Free Hands-On Guide to API Testing Course

What is Headless Testing

Most headless testing consists of bypassing the GUI and sending a request directly to an application’s backend or service and receiving a response back while validating the response to ensure things are working as one expects them

The above example is often referred to as the client/server relationship. A client makes a request by asking for a resource, and the request goes out to find the server that will fulfill the request. The server locates the desired resource and then sends a response back to the client.

Why is API Testing Important?

With Agile development becoming the standard in most organizations, the ways in which we develop software and automate tests have changed dramatically.

Pre-Agile, most of the time spent on automation was done against a graphical user interface (GUI). This is the piece that tools like Selenium and  UFT/QTP handle.

But if you’ve been doing automation for any length of time you know how time-consuming, fragile and hard-to-maintain these types of tests are.

Entire books have been written on how organizations have invested large sums of money into creating custom functional GUI test automation frameworks, only to become frustrated with their reliability over time; to the point where people stop using it and the software system becomes shelf-ware.

Also, GUI tests that go against a user interface tend to take a long time to run. For certain Agile practices like continuous builds, when new code is checked in, the amount of time it takes to receive feedback from a GUI regression suite of tests is unacceptable.

What are the benefits of API testing?

API testing offers a wide range of benefits crucial for ensuring the reliability and performance of software applications that rely on APIs. Key advantages include enhancing test coverage and efficiency, guaranteeing functionality, performance, security, and compatibility.

By frequently running API tests as part of DevOps processes or CI/CD pipelines, development teams can streamline their release cycles and focus on core aspects of software development.

Additionally, the shift-left approach of API testing allows for early issue detection, leading to faster bug fixes and overall improved efficiency in identifying performance bottlenecks and scalability issues. Moreover, the support for various programming languages and the provision of clear documentation for API usage promote better collaboration among development teams and help in ensuring data security by identifying vulnerabilities and implementing necessary security measures.

But one of the biggest benefits to me is faster feedback.

API Fast Feedback

In those cases, quicker feedback is needed.

The sooner bugs are found the better since a developer instantly knows the code changes they made have broken the build and need to be looked at. In test-driven processes, users need a large percentage of test sets to run fast and frequently and must be able to integrate them into the development lifecycle.

Don’t get me wrong — GUI testing is still very important; it’s the only test type that truly tests how a user will experience an application during production. Certain defects can only be caught by GUI tests. In other words, while it’s crucial, GUI should not be the only type of automation a user focuses on, nor should it be the largest piece of the total amount of automated tests that one creates.

All the reasons I just listed have given test automation a reputation for being unreliable and not worth the effort to create. Right now you may be thinking, “This stinks! Isn’t test automation a core agile practice?!?” No worries! Luckily, the type of automation Agile focuses on is Unit testing (and the more reliable API lower-level testing) and less on GUI automation.

What is the API Testing Pyramid

In his book Agile: Software Development Using Scrum, author Mike Cohn introduces the concept of a test automation pyramid:

This image represents the opposite of the way most non-agile development teams perform automated testing.

What is a GUI Test

GUI testing focuses on testing an application user interface to ensure that its functionality is correct. IDE UI tests are