4 Important Things You Should Be Testing Your APIs For

Testing is one of the most important parts of the API lifecycle. But it is also one of the hardest parts to work on for the sheer complexity of what an API tester deals with. Compared to the role of a developer, the role of an API tester is more difficult. The latter is compelled to test the API beyond basic functionality. Duties include seeing how the API’s components sync up from end to end, dealing with the API’s security issues, and other advanced problem-solving tasks. To accomplish all of these successfully, a tester would need both a comprehensive API testing tool and a focused approach on what to test for.

With that said, what should your own approach to testing be like? What should your API testing metrics be based on? Here’s a list of four considerations that will likely make the API testing process easier for you.

Can Your API Accomplish What It’s Set Out to Do?

The simple question that should be at the forefront of your testing is this: what is your API going to be used for? We use APIs on a daily basis, such as by linking social media content or using digital payment functions on ecommerce sites. These APIs fulfill the basic function of letting two applications communicate with each other.

So when you feel like you’re losing sight of why you’re testing, go back to this central question. Let this serve as a sort of mission statement to guide you through the various phases of testing, from mocking to virtualization.

Can Your API Handle the Load You Want It To?

Another parameter that you should test for is load, as your finished API product must be able to handle a lot of calls. One of your critical duties as a tester is to see how the API can hold up against progressively higher loads. And among other key metrics, you should be measuring the API’s throughput, or number of transactions per test period, and response time for each request.

Load testing is a crucial way of figuring out your API’s limits. Just take care to avoid what API experts call the most common rookie mistake: to always assume the best out of each load scenario.

How Compatible is Your API with Other Operating Systems, Browsers, and Devices?

The very description of APIs involves connection. A successful API will not only be able to connect two applications, but integrate seamlessly into the vast digital ecosystem it’s part of.

That ecosystem includes different operating systems, browsers, and devices. See if your API can integrate with every OS, web browser, or mobile device that you mean for it to.

Can the API Withstand All Possible Wrong Inputs from Users?

Handling less-than-ideal inputs is the purpose of negative testing in API development. What happens when your API incurs a user-related or UI-related problem? Will it be able to deal with every wrong input it could possibly come across after its launch?

Negative testing isn’t just for measuring the API’s performance. It’s a means of checking the API’s resilience to security issues as well. Erroneous input isn’t the only thing you might have to worry about—hackers with malicious intent may try to breach your API. But if your negative testing is thorough enough, you’ll have predicted the worst-case scenario in advance and figured out a way to respond to it.


Hopefully, this checklist has served its purpose in assessing how ready your API is for its eventual launch and adoption by a client. As an API tester, don’t lose sight of the goal: more than going through the motions of testing, you should commit to testing purposefully.

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