API Testing

Last Updated on March 6, 2024 by Nadeem Ahmed

The term “application programming interface” (API) is an acronym. There is a layer called API between the database layers and presentation in application development. The primary purpose of API is to enable data transmission and communication between systems.

Software testing is unfeasible because of the shortage of a graphical user interface. The message layer, which includes REST API and SOAP services that are transferable through HTTP, HTTPS, JMS, and MQ, is the focus of API testing. This is a necessary part of every automation testing nowadays.

The testing of API cannot be performed manually as it requires the use of specific code. Therefore, some testing tools are needed. This post covers approaches and tools of API testing. Before we dive into it, let’s begin with an overview.   

What is API Testing?

All QA testing activities include sending API queries, generating output, validating system response, and validating system output against predetermined input criteria, such as data format accuracy and information, error codes, and HTTP code. The technique used to test APIs depends on the type of API.

Using web APIs, sometimes referred to as web services, allow you to access resources that are not on the same device as you are. Database APIs also link the application to a database management system. 

Approaches to API Testing

It took a while for remote APIs to evolve from simpler local APIs that programs could use to run on the same machine. Remote APIs allow programs on one computer to call up apps on another.

The QA team may use these types of API approaches. No list could ever contain every specialty test because so many of them exist.

  1. Unit testing: Writing API tests for each new release of an application is a practice known as unit testing. For the program to pass a build, it should be written near the code. How much code coverage is necessary, and does it depend on the features it delivers and the level of risk it poses? Considering this API testing area is essential because it will benefit the remaining work in the future.
  1. Integration testing: Effective API integration testing is necessary for prior planning. Testing your API integrations is essential to ensure that your product’s functionality is not compromised. The effectiveness of the application has a significant impact on the user experience. 

Users’ opinions of your product will determine whether it succeeds or fails. API integration tests are challenging and contentious because of their size, structure, and constant expansion. Contrarily, the benefits include quicker production of goods of higher quality, which makes it challenging to accept.

  1. Security testing: This test guarantees that external dangers are kept out of the software development process’s API testing and implementation phases. 

Additionally, procedures like API access control architecture and encryption technology validation are part of API security testing. Additionally, it manages user rights and verifies authorizations.

  1. Performance testing: During this API performance test, the program’s responsiveness, dependability, speed, and functionality are evaluated. This ensures optimal effectiveness as a result. Instead of looking for weaknesses, this test seeks explicitly to remove software performance bottlenecks.
  1. Load testing: This non-functional exam helps evaluate a product’s usability and effectiveness. End-to-end API testing for software development is made available in real-time so that many people can test it simultaneously. Load testing enables the developer to appreciate the program’s operating capabilities, evaluate the app’s usability under heavy load, and ascertain the app’s expansion potential to handle additional users.

API Testing Tools

The tools that assist in automating the procedure of testing API are mentioned below:

  • Postman: Postman is an API development and consumption tool. Because it simplifies each stage of the API lifecycle and streamlines cooperation, designing APIs is quicker and more efficient. It was once a Chrome extension. On-premise Postman API testing is now available for Windows and Mac.
  • JMeter: Although Apache JMeter was created for performance testing, it is commonly used for functional API testing. JMeter has all the functionality you might need to test APIs and several other tools that can enhance your API testing efforts.
  • Katalon Studio: Katalon Studio is the most comprehensive and dependable automated testing solution. Katalon is a Software Test Automation for API, Web, and Mobile Applications Gartner Peer Insight Customers’ Choice.
  • Test grid: The following option for API testing is Test Grid. It is a Web API development package and has an easy-to-use user interface. You can develop and implement test cases with the help of your business team without any prior programming experience. This accelerates the API procedure by 70% compared to typical APIs.
  • SOAP UI: SoapUI is a well-known API testing tool. This headless functional testing tool’s primary goal is API testing. Users can quickly test SOAP, REST, and Web Services using this API tester.


Hopefully, you have gained a better grasp of API testing, its approaches, and its tools. API is critical when regarded from both the business and software perspectives. Depending on your requirements, every API testing tool works well and is a great option.

Apart form this if you are interested to know about more UX Research Jobs then visit our BUSINESS category