API testing is software testing that evaluates the advanced API (application program interface) within the website to verify its potency to function according to its features. API web services testing evaluates the features like performance, reliability, and security and their associated functioning.

These are either directly or through integration testing or the inbuilt advanced API. API is an application programming interface that runs through a unique middleware code that enables the communication medium through dual software programs.

This inbuilt coding usually defines the specification and method by which the particular application demands the required services from a particular operating system (OS) or other applications. Further, in this blog, we will discuss more API testing and its usage.

API Testing: Overview

An application normally runs on three levels: a data functioning layer, the application service layer, the API functional layer, the core presentation layer, and the final user interface (UI) layer. Any business that runs with a detailed logic of building an application must monitor how users’ interaction is running with the inbuilt functions, data, and services integrated within the app in the API layer.

API testing primarily focuses on evaluating the business logic and security functions of the application and detailed data reports. These tests are usually accomplished by producing special requests to multiple API endpoints. The requests are further compared with the reaction according to the anticipated outcomes.

Categories of API Testing:

Several types of API testing are used to safeguard and monitor the user interface and application run on a practical platform with appropriate functionality. The testing interface ranges from common to specialized evaluation of the particular software. Below are some of the different categories of API testing mentioned:

  • Security testing: This is the most important API testing service under its categories. It is an advanced security audit procedure that incorporates validating and testing the accessibility of control design with an encryption procedure of the API. API security testing further validates.
  • Functional testing: This type of API testing evaluates the API functions according to its codebase. It tests the functions according to the estimated parameters of error handling with its projected outcome.
  • Reliability testing: This test functions with API-based automation, which confirms the stable correlation of running platforms remains persistent and thus achieves the coherent conclusions of API testing.
  • Validation testing: This type of API testing services includes the testing of the entire software development project with its built quality, the potency of the designed API, produced code quality, and other related aspects. The validation testing also comprehensively focuses on API’s behavior, accessibility, storage, and security interface. In addition, it analyses the API efficiency, accuracy, and certain impairments which can impact overall services.
  • Load testing: The load testing evaluates the call handling capacity for API end-to-end testing. It determines the practical or theoretical solution performing under the designed API capacity. This type of test can be performed with the complete codebase of a particular unit.

Use of API Testing Tools:

API testing tools are an integral part of software programming and quality testing. The API testing company facilitates and supports the new-age developers for convenient testing deployment. It provides customer-responsive interfaces with all the essential coding requirements.

A wide range of API testing tools are available to test, with open source offers to paid subscription tools. Several API testing tools are developed to analyse the common API issues that usually pass undetected with standard API testing. Below are the popular API testing tools mentioned:

  • REST Assured: It is another open-source API testing tool with advanced Java-supported language that enables and simplifies API testing.
  • Postman: It is a Google chrome app functioning as the API testing tool ultimately used to automate and verify the API testing.
  • Apache JMeter: It is an open-source API tool for functioning and loading API testing.
  • Swagger UI: This API testing tool utilizes the documented APIs and is an open-source tool that generates the multifunctional webpage.
  • SoapUI: This API tool aims to test the core API functions under REST and SOAP APIs for the performance testing for API.
  • Katalon:This API testing tool with UI automated testing functions as an open-source API testing application.
  • Apigee: This is a high-end API cloud testing tool designed by Google with a core emphasis on testing the performance of an API.


It is detailed information about API testing and its integrated tools for advanced quality testing. The process of API testing is commonly automated and utilized by advanced systems such as development teams, DevOps, and quality assurance (QA) to monitor the uninterrupted testing systems.