API Testing Types – A Comprehensive Guide

API Testing Types

Last Updated on October 1, 2023 by Team Experts

Ever since the world has adopted the digital transformation goals, APIs have become more significant than ever. Everything that you see, share, or communicate is being transmitted over the Internet with the help of APIs.  

And therefore, when integrated into modern IT solutions, it becomes necessary to foster API testing. It is vital that APIs like any other functionality must be evaluated on the quality attributes to ensure optimum performance. The process includes keeping a check on functional requirements as well as all the non-functional factors.  

In this blog, we will aim at highlighting all the API testing types that can help create a sustainable IT solution. On top of that, we will talk about the definition of API, its advantages, and other essential details that can help you foster API testing with ease.  

API Testing: Definition & Importance 

In general, API or Application Programming Interface is meant to connect two different software systems and allow exchange of data. Moreover, software with API can perform many functions compared to other software systems.  

An API could explain the types of requests that can be made, how they can be made, and the data formats which must be used to transfer information between two systems. Thus, the entire purpose of using APIs is to drive security. Unlike standard user inputs/outputs, API testing services makes software to send calls to the API in order to receive production and record system response. 

Coming to API testing, it is a process very different from GUI testing as it does not focus on the app appearance but works on software architecture’s business logic layer.  

Importance of API Testing 

Language Extension 

Since data exchange is made with JSON and XML, automation can be done using any language, irrespective of which language was used to develop the application. Moreover, XML and JSON are structured data which allows stable and rapid verification. Moreover, they bring along built-in libraries to aid data comparison for the available data formats.  

GUI Independence  

Another significant advantage of API is accessing the application without UI. It means QA testers can run API tests without knowledge of the applications. It gives early visibility to QA engineers to look into errors and faults without affecting GUI.  

Added Speed & Coverage 

API testing not only brings the normal UI regression test suite that takes 8-10 hours to 1 to 2 hours but even aids in creating automated tests with high coverage on functional and non-functional testing.  

GUI Integration 

API testing allows the most integrable tests. For instance, if you need to run GUI tests after API testing, it allows you to introduce new users within an existing program before GUI testing begins. 

Automation & Core Functionality Testing 

Last but not least, API testing allows an early assessment of the build strength of the app under test while cutting any flaws that can hamper future performance. Moreover, API testing brings you so many toolkits and frameworks to automate API requests enabling API test automation suite building. 

Types of API Testing 

To put it in words, API testing as a practice allows early identification of bugs and defects while saving you money and time. And therefore, it becomes necessary to understand the types of API testing in order to ensure maximum benefit of the technique. 

Validation Testing 

Validation testing is one of the last stages of the development process. Validation testing is the application of simple queries to the product. These include product-related, behavior-related, and efficiency related queries.  

It aims at ensuring that the right product is built? Is the API accessing the data correctly? Is the API working precisely and efficiently? 

UI Testing 

Though validation and functional testing are universal practices, UI testing is more of a particular task. It works on checking the user interface for API and its components. It is usually done to check the usability and efficiency of the API at both front-end and back-end. 

Functional Testing 

Narrower than validation, functional testing is meant to check the codebase to guarantee API functions satisfy the expected parameters. It is meant to ensure that any errors found must be handled appropriately when desired parameters are not attained.  

Load Testing 

Driven by realism, load testing aims at removing errors in practical, to ensure the application works smoothly under the given load. Usually worked after working on a unit or codebase, it helps to work on peak performance scenarios of yielding API capabilities.  

Security Testing 

Implemented to secure API implementation from outside threats, security testing aims at the use of encryption technologies and the architecture of the API. Besides, it works on user privileges and validating authorizations.  

Penetration Testing 

Penetration testing works by analyzing the threat vector from outside. The process works at testing functions, resources, and processes including the whole API components at times.  

Fuzz Testing 

Fuzz testing is the part of security auditing where a large amount of random data is allowed to enter the system. The system is then checked for any crashes or unexpected behavior of the API. 

Performance Testing 

Unlike regular load testing that works at implementing the CI/CD setup, Performance testing works on ready API for RESTful, SOAP, and other web services that help integrate optimal performance for the CI/CD workflow.  

End-to-end Testing 

Used to check app functionality and performance under live-like conditions, the end-to-end testing of APIs work at recreating real-world scenario from beginning to the end. This type of testing ensures the accurate and efficient functioning of product subsystems.  

Component Testing 

Component testing as its name suggests works on checking different system components without integration with other elements. It is also known as module testing as it works on testing of units, programs, and modules of the entire system.  

Scenario Testing 

Scenario testing is a software testing technique that works on scenarios or speculations. It works on checking the system problems, process flows, and other factors that can help confirm the product to be convincing and dependable.  

Omni-Channel Testing 

Lastly, API testing ends with omnichannel testing i.e. checking the app on different devices and platforms in order to yield a uniform and seamless digital experience.  

The Crux 

Implementing API testing needs careful consideration to organize API test cases into the right test categories. The process thus needs to include the declarations of the APIs at the top of each test to align with the parameters correctly. More importantly, it is necessary that API function calls must be prioritized for quick testing while checking each test case must be self-contained and feasible. 

Also, making your API testing initiatives a success needs you to avoid any test chaining. Rather the testers should give special attention to dealing with one-time call functions. It requires performing call sequencing and meticulous planning but it is vital to create API test cases for all conceivable combinations of the API to yield maximum test coverage.  

Read more: Top Industries That Are Boosting Rapidly Worldwide

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Anil is an enthusiastic, self-motivated, reliable person who is a Technology evangelist. He's always been fascinated at work especially at innovation that causes benefit to the students, working professionals or the companies. Being unique and thinking Innovative is what he loves the most, supporting his thoughts he will be ahead for any change valuing social responsibility with a reprising innovation. His interest in various fields and the urge to explore, led him to find places to put himself to work and design things than just learning. Follow him on LinkedIn

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