Why API Testing is Important

Getting started with API testing

Here at SoapUI.org, we are committed to making API testing easy and reliable for everyone. We believe that API testing is a crucial part of the API development lifecycle, and that it should not be forgotten. We’re glad you’re taking the first step towards testing your APIs, learning more about the process! API testing can be a daunting task if you aren’t quite sure where to start. We have the resources you need to understand how to test your APIs and how to make sure they are successful. API testing could be one of the most challenging parts of software and QA testing because APIs can be complicated, they are often based on protocols and standards that we often do no encounter in other kinds of testing. While developers tend to test only the basic functionality they are working on, testers are in charge of testing functionality, performance and security of APIs, discovering how all components  work together from end to end.

Why is API testing important?

At its most basic level, testing is intended to reveal bugs: inconsistencies or deviations from the expected behavior. Back in the day, developers did just enough to prove the software worked – they only checked that their software did what they thought it was supposed to do. That was all the testing that was done, and there are companies even today that still believe this is all that is needed. This is not testing, this is only checking your assumptions. Here are some of the most common reasons people test their APIs:

  1. Make sure it does what it’s supposed to do
  2. Make sure it can handle the load
  3. Find all the way users can mess things up
  4. Make sure your APIs work across devices, browsers, and operating systems
  5. It can be costly not to

Putting more effort into API testing leads to a much healthier final product. Ensuring that all data access (read and write) goes only through the API significantly simplifies security and compliance testing and thereby certification, since there is only one interface.

Ensuring that all the required business rules are being enforced at the API tier allows time for much more complete user-experience tests once the UI is released, and not having to concentrate on testing every single business rule and path through the application near the end of the project. Ensuring that the API offers complete functionality allows for easy future expansion of the application as new business needs arise.


What you need to start API testing

The first part of API testing involves setting up a testing environment, with the required set of parameters around the API. This involves configuring the database and server for the application’s requirements. Once you’ve set up your API testing environment, make an API call right away to make sure nothing is broken before you go forward to start your more thorough testing.

You can start combining your application data with your API tests to ensure that the API performs as expected against possible known input configurations. See this REST Testing example for beginners to help with the visualization.

Next, you need to organize yourself around the API test. Start by asking yourself these questions:

  • Who is your target audience? Who is your API consumer?
  • What environment/s should the API typically be used?
  • What aspects are you testing?
  • What problems are we testing for?
  • What are your priorities to test?
  • What is supposed to happen in normal circumstances?
  • What could potentially happen in abnormal circumstances?
  • What is defined as a Pass or a Fail? What data is the desired output? What is the chain of events?
  • What other APIs could this API interact with?
  • Who on your team is in charge of testing what?

After you’ve created these testing boundaries and requirements, you need to decide what you want to test your API for.


What types of API testing can I do?

  • Functionality testing — the API works and does exactly what it’s supposed to do.
  • Reliability testing — the API can be consistently connected to and lead to consistent results
  • Load testing — the API can handle a large amount of calls
  • Creativity testing — the API can handle being used in different ways.
  • Security testing — the API has defined security requirements including authentication, permissions and access controls. See some API security tips for protecting vital data
  • Proficiency testing — the API increases what developers are able to do.
  • API documentation testing — also called discovery testing, the API documentation easily guides the user.

The kinds of tests you will run will vary, but these are common API test examples, as you can see, they are very similar to the reasons why you would want to test your API:

  • Checking API return values based on the input condition
  • Verifying if the API doesn’t return anything at all or the wrong results
  • Verifying if the API triggers some other event or calls another API
  • Verifying if the API is updating any data structures.


Start testing your APIs today

SoapUI Pro provides the industry's most comprehensive and easy-to-learn API testing capabilities. Based on open core technology proven by millions of community members, SoapUI Pro helps you ensure that your APIs perform as intended, meet your business requirements, timeframes, and team skill sets right from day one.

It’s loaded with advanced technologies and features you won’t find in other test tools. The all-in-one automated SOAP and REST API testing tool that's one of a kind.

To get started with API testing, download SoapUI Pro