Overview of API Testing Tools 2020

DZone 's Guide to

Overview of API Testing Tools 2020

APIs keep software functioning and ensures seamless communication between various systems. Learn what tools will help to run API testing efficiently.

· Integration Zone ·
Free Resource

Modern software has a complex multilayered architecture, where APIs ensure seamless integration between different systems. API testing allows you to check the core functionality of an application at the earliest stages. On the one hand, QA engineers don’t even need a ready user interface to start testing. On the other hand, it is a way to detect bugs that can cause serious issues during GUI testing. For sure, API testing is essential, and the following tools will help a QA team to run it efficiently.

Tools for Manual API Testing


The tool is positioned as a collaboration platform for API development. It simplifies and facilitates the process of building an API. Postman is a good choice for those who don’t want to deal with integrated development using the same language as developers. 


  • Allows running requests, testing & debugging, documenting, and monitoring APIs. 
  • Can extract almost all web API data. 
  • Assists in exploratory testing. 
  • Provides rich collaboration features. 

Platforms: Windows, Mac, Linux, Chrome browser-plugin.

Pricing: a free version and three paid plans. 


This tool is completely dedicated to API testing. The platform provides a list of resources that help you get started with API testing. SoapUI is used by many world-leading tech companies, including Apple, Microsoft, Oracle, NASA, and Cisco. 


  • Makes it easy to create, execute, and manage end-to-end tests.
  • Supports data-driven testing, reading data from files and databases. 
  • Integrates with over a dozen of API management platforms. 
  • Allows adding custom functionality or workflows (written on Groovy).

Platforms: Windows, Mac, Linux.

Pricing: free and pro versions available.


Katalon is better known as a tool for GUI test automation, but it is also used in exploratory testing – API testing, in particular. Katalon is a perfect tool for beginners since it is easy to set up and learn. This tool was featured as one of 2020 Gartner Peer Insights Customers’ Choices, receiving over 600 positive reviews. 


  • Supports data-driven testing, CI/CD integrations, and the AssertJ library. 
  • Suitable for both beginners and experienced users.
  • Supports combinations tests balancing on the verge of UI and API testing. 
  • Provides sample projects for reference, API testing examples, and lots of user guidelines.

Platforms: Windows, Mac, Linux.

Pricing: a free version and two paid plans.


Tools for Automated API Testing

REST Assured

To start with, you can find two variants of spelling – REST Assured and REST-assured; both are used even on the official website. Nevertheless, this doesn’t change the fact that REST Assured is one of the most widely used API automation testing tools that greatly simplify the check of Java domain services. 


  • Users don’t have to write code from scratch thanks to baked-in functionalities. 
  • Supports behavior-driven syntax, as well as XML and JSON Request/Responses. 
  • Seamless integration with the Serenity framework to combine UI and API tests and generate clear reports. 

Programming language: Java.

Pricing: Open-source.


Frisby is a testing framework built on Node.js and Jasmine for easy and fast testing of API endpoints. It requires minimum setup to run a test and can run tests in parallel.


  • Comes with many built-in features that cover different aspects of API testing.
  • Allows customizing and extending assertions to make the scenarios more efficient. 
  • Supports behavior-driven testing. 
  • Can run in CI mode and delivery pipeline.

Programming language: JavaScript.

Pricing: Open-source.


CodeceptJS is a multi-backend tool for end-to-end testing and one more tool for JavaScript API testing. The tests are easy to create since they are written as a sequence of actions from a user perspective. In addition to simplicity and functionality, users get beautiful reports. 


  • Supports scenario-driven and behavior-driven testing. 
  • Executes tests using different libraries.
  • Runs parallel tests, splitting big tests in chunks and inspecting each part separately, and multi-session tests in several browser windows. 
  • Enabled with an interactive console and synchronous recording feature.

Programming language: JavaScript.

Pricing: open source.


Requests is an HTTP library for Python – a pre-configured collection of routines, functions, and operations a program can use. So what is it doing on this list? Created by enthusiasts and developed by everyone willing to contribute, it makes HTTP requests human-friendly, and API testing with Python becomes highly efficient. 

Requests package provides a set of commands you can use efficiently to examine communication between different systems. Users don’t have to add query strings to URLs manually or form-encode your POST data, and the commands don’t slow down the application under test. Thus, API automation using Python might be the simplest way to run tests. 


  • Lets users add headers, form data, and multipart files via simple libraries. 
  • Allows accessing the response data in the same way. 
  • Works with international domains, sessions with cookie persistence, proxies, and much more. 
  • Comes with a variety of useful third-party extensions.

Programming language: Python. 

Pricing: Open-source.


RestSharp is one more HTTP client library – the most popular one for .NET framework. It allows quickly accessing API data, leaving out the complexity of dealing with raw HTTP requests. Though used mainly by OSS projects, RestSharp has been downloaded over 32 million times. 


  • Easy to install and has a clear interface. 
  • Custom serialization and deserialization. 
  • Automatic XML and JSON parsing, inc. fuzzy element name matching.
  • Offers a variety of authentication features and extensive configurations.

Programming language: C#.

Pricing: Open-source.


How to Choose the Best Tools for API Testing?

What to consider when choosing tools for API testing? Start with the most obvious thing: tool popularity. The most widely-used tools are usually the most reliable and functional ones. Then, answer the following questions: 

  • Do you plan to run manual or automated tests? 
  • What platforms and environments does the tool support? 
  • On what technology is the software built? 
  • Is the tool complicated to use? 
  • If yes, do you have resources for learning or educating the team to use it? 
  • Do you need an open-source option or a paid tool will do, too? 
  • Do you prefer a development or runtime license? 
  • Does the price justify the functionality?

Bottom Line

This list is far from complete, but the tools I’ve mentioned often pop up during discussions of the best practices of API testing. Our team uses many of them, too. Hopefully, you’ll find a solution that fits your needs best. Keep experimenting and try working with different tools until you do.

api, api testing, api testing tools, automated testing, integration, qa and testing, quality assuarance, test automation, testing tools

Published at DZone with permission of Vlad Ershov . See the original article here.

Opinions expressed by DZone contributors are their own.

{{ parent.title || parent.header.title}}

{{ parent.tldr }}

{{ parent.urlSource.name }}