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A Guide to API Testing

Val Pliskin
By Val Pliskin
5 min read
A Guide to API Testing

API testing will never make a Top Five Tests Developers Need to Perform list. Yet, as developers continue to use microservices to rapidly develop software, APIs function as a critical doorway. They connect functionality from multiple microservices into a single piece of software. 

As a result, APIs are a part of every piece of software we use today. API testing helps to ensure that software meets the design requirements for performance, security, functionality, and dependability. The tests are fast, deliver high ROI, simplify the validation of business logic, and prevent software regression by verifying that all your services speak the same language. They enable engineers to detect integration faults early-on and test services in isolation to develop and advance them independently.

While some developers use UI-based tests, API testing results are more reliable and can be completed faster and cheaper. 

API tests differ from UI-tests in other ways as well. Rather than using standard keyboard inputs and outputs, testers use software to send calls to the API, which takes place at the message layer. The output is received and tracked. It doesn’t focus on the look and feel of the application; its area of focus is on the business logic layer of the application.


The Errors API Testing Detects

API testing will help developers find a number of different software bugs.  It alerts them to unused flags, as well as missing or duplicated functionality. If there are any multithreading issues, these tests will alert you to them. 

Tests also reveal reliability issues. API testing looks at the ease or difficulty in connecting and getting a response from the API. At the same time, it looks at performance issues, including response time and response data structures. 

API tests can highlight security issues, improper errors, warnings to callers, incorrect handling of valid argument values, and the failure to handle error conditions. 

What API Testing Can Demonstrate

API test results provide developers with answers to key questions in their software development. Results show whether the software is usable and easy to set up, as well as whether or not it works as expected. 

Your results will let you know if the software is reliable over long periods of time, and if it is performing as expected. Results can also lead testers to find new ways of using their APIs. Lastly, testing should reveal if the software is secure enough to be used. 

Different Types of API Testing

As you might expect, there are a number of different API tests that developers need to run. 

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Performance Testing – while some tests focus on defects, performance testing helps developers find and eliminate performance-blocking elements within the software. It involves checking response times, reliability, functionality, and speed. 

Load Testing – this simulates real-world conditions to see if the API can perform when multiple users are running the software concurrently. 

Runtime Error Detection – this test focuses on errors that occur while the software is running, and includes the implementation of testing elements that attempt to expose glitches. 

Security Testing – this enables testers to uncover vulnerabilities or threats to the software by hackers and malicious attacks.

Interoperability Testing – this test checks whether the software can intermingle with other components without concern of any compatibility issues. 

Penetration Testing – working as a simulated attack against the software, this test helps developers identify weaknesses that an attacker can take advantage of once the software is released. It provides a roadmap on what to look for in potential future breaches.

Fuzz Tests – this tests the limits of what software can handle when facing fuzz or noise before it crashes, and checks that there aren’t any potential memory leaks.      

Reliability Testing – this test provides developers with an understanding of the overall reliability of getting the data requested from the API for all APIs. It checks whether the software can perform with any failures over a set period of time in a specific environment.

Usability Testing – usability tests that look at the API from the perspective of the user, and demonstrates how usable the APIs actually are. 

Omnichannel Testing – this tests the APIs on different channels, such as web, mobile, and other devices.

End-to-end Testing – this test looks at the entire software entity, and ensures that all APIs within the application are performing as designed. 

before you begin

It’s important to understand your API requirements before you begin testing. Start by defining the purpose of each API being tested, which will enable you to define your verification approach. For some APIs, you’ll verify responses against the database, while others will make more sense to verify against similar APIs. 

When designing API tests, you’ll also need to design both positive and negative tests. This will provide you with visibility into the overall working of the API. Positive test results should verify that the API received the input and returned the expected output. Negative results, on the other hand, should give you the expected non-response to an input that does not meet the API’s requirements. 

When designing your testing plan, take care not to overlook small functional APIs, such as Login or Get Token APIs. These simple APIs are gateways to the more complex APIs and ensuring that they are functioning properly guarantees they won’t interfere with your more complex API tests. 

The Bottom Line

As you can see, API testing brings tremendous value to the developer. It helps increase the pace of development by showing exactly where issues are occurring and guides developers to faster fixes. As a result, this can improve time to market, enabling companies to get their software applications into the hands of their users faster. 

API Testing with Seekret

Tests can easily scale as needs arise and as your business continues to grow. Auto-generate API tests with Seekret and enable your developers to conduct more tests in a shorter time period, as well as track and analyze results. Book a demo today to see us in action!