API Testing Tools and Automation Essential Guide

  • Updated on April 25, 2022
  • Tech

Application Programming Interface is the term used to refer to APIs. Communication between applications is typically facilitated through APIs, which can facilitate communication via any mode of communication. 

API automation can aid in the acceleration and efficiency of integration API testing. Given that most businesses now use Restful microservices/APIs at the business layer, API Testing Tools has become a critical component of any release’s test plan. API is a service that enables the communication of two separate applications. 

In other words, the API is the central nervous system of our networked world. APIs enable businesses to become more agile, things to go mobile, and everything to work together in a streamlined, integrated manner due to their dynamic nature and capabilities. Thus, API Testing encompasses both service-level and integration-level testing.

Testing Strategy for API: 

The tester should make API calls with software to obtain output before observing and logging the system’s response. Most importantly, it ensures that the API responds or outputs correctly under various conditions. Typically, this output is one of the following three:

  • A successful or unsuccessful status 
  • Data or information 
  • A call to another API

However, there is a possibility that there will be no output or something completely unexpected will occur. This highlights the critical nature of the tester’s role in the application development process. Additionally, because APIs serve as the central repository for data in many applications, data-driven testing can increase test coverage and accuracy.

Specifying pass/fail scenarios is slightly more challenging when testing the API directly. However, comparing the API data in the response or the behavior of another API following the API call would assist you in setting up ideal validation scenarios.

While developers typically test only the functionalities on which they are currently working, testers are responsible for testing individual functionalities and a series or chain of functionalities to determine how they interact from beginning to end.

Purpose of API Testing

Agile has become the standard for developing software and automating tests, in most organizations. Before Agile, most time spent automating was spent against a graphical user interface. However, anyone who has worked with automation for any time understands how time-consuming, fragile, and challenging it to maintain these types of tests are. GUI tests run against a user interface typically take a long time to complete. It is unacceptable that a GUI regression tests suite must be run for every new line of code that is checked in using certain agile practices, such as continuous builds.

Different Types of API Testing-

First, determine the type of API Testing Tools or API tests you require. Just as testers perform various kinds of testing on their product’s features, APIs perform similar tests. API testing frequently entails the following:

Unit Testing

To validate the functionality of single operations. For instance, Google offers a geocoding API that can determine the longitude and latitude of any location. Typically, this takes an address as input and outputs lat longs. Now, when unit testing this API, the tester can pass various locations and verify the result.

Functional Testing

This type of testing is primarily concerned with the API’s functionality. For example, this would include test cases to verify HTTP response codes, response validation, and error codes if the API returns an error, among other things.

Load Testing

This type of test is necessary when an API deals with a large amount of data. There is a possibility that many users will use the application concurrently. This increases API calls concurrently, and the application may crash if it cannot handle the increased load.

Security Testing

Security testing is critical because APIs connect two separate applications. The primary goal is to abstract or conceal the application’s database from other applications. This could include test cases involving authorization checks and session management.

Interoperability Testing

This ensures that the API is accessible to the appropriate applications. This is true for SOAP APIs.

WS compliance testing

APIs are tested to ensure that standards such as WS-Addressing, WS-Discovery, WS-Federation, WS-Policy, WS-Security, and WS-Trust are implemented and used correctly.

Penetration Testing

This determines whether an API is vulnerable to attack from external sources.


API-based applications are becoming increasingly popular these days, according to industry experts. Compared to traditional software, these applications are more scalable and have more straightforward integration with other APIs. As a result, API testing adds a higher level of value to a product than a standard manual or automated testing technique would. Thus, it is possible to improve quality at a higher level and achieve our testing objectives by employing the proper tools and configuration.


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