Which is best for API Automation?

Best API Automation Testing Tools

The Best API Automation Testing Tools

API testing is a type of software testing that looks to see if APIs are up to par. Typically API testing is becoming increasingly crucial for programmers and developers as APIs become a fundamental part of software development. APIs (application program interfaces) do not have a visual user interface; thus, this testing cannot be done on the front end.  In this post, we will review the best API automation testing tools and outline their benefits and shortcomings so that you can make a wise, informed decision by the end of this post. But, before we jump on the list, let us first look at the basics of API automation testing tools. 

Table of contents:

  • What is an API?
  • What is API testing?
  • Importance of test automation through a test pyramid
  • Best API testing tools
  • How to choose API testing tools
  • FAQS: Which is the best API automation tool?

What is an API?

APIs is an acronym for Application Programming Interfaces. It allows applications to interact and communicate with each other by establishing precise regulations and determinations. Mainly, they are accountable for stipulating the types of requests that software can make to another and for defining the following three aspects:

  1. What practices the user must follow
  2. In what data formats can you make requests
  3. How to make requests

Thanks to APIs, an application connected to the internet can send the request (with data) to a server, and, in turn, the server will retrieve the request and interpret it. When the necessary actions are executed, it sends a response back to the software’s user interface with information. 

What is API testing?

What is API testing

API testing comprises software that tests how the APIs were developed. It analyzes if the APIs correctly fulfill their purpose to ensure the application’s performance, security, reliability, and functionality are not compromised. Besides, API testing mainly consists of testing REST APIs and SOAP web services using JSON or XML message payloads sent via JMS, MQ, HTTP, and HTTPS. 

API testing tools enable testers to verify numerous aspects, including:

  • The time it takes to deliver a response
  • If it responds securely to possible security attacks
  • If it reacts adequately to edge cases (i.e., failures and unexpected inputs)
  • If an API is returning the anticipated response and in the correct format

What are API automation testing tools?

API testing, also called application programming interface testing, is a type of software testing that evaluates the quality of development APIs and determines if they meet performance, functionality, and security requirements. There has been an advancement in interest in API/Web services testing. Having an efficient strategy and the right tools for API automation tests is becoming increasingly essential. API is vital for a successful DevOps/CI practice.  The best API testing tools are outlined in this post, which ranges from commercial solutions to open-source tools based on the demands of testing teams. 

Importance of test automation through a test pyramid

In general, the ROI for the API testing will be higher when compared to the other testing types performed by the testers.  In the test pyramid, API tests are in the second layer, and it requires 20-percent of testing efforts. While testing an API, the focus should be on utilizing the software so that the API will be called. 

Thus, you need to check if the API will return the correct output under different conditions during testing. The output in which the API returns is typically the fail or pass status or a call to another API. For test coverage and more accuracy in API, data-driven testing should be performed.  To test the API, testers prefer automation testing compared to manual testing. This is because manual testing of APIs includes code writing to test it. API testing is performed at the message layer as GUI testing is absent. 

Before you begin API testing, you need to set up the test environment with parameters. Configure the server and database as per the requirement. Then just like we carry out smoke testing for a solution, check the API by making an API call. This step will ascertain that nothing is broken, and you continue for thorough testing. The various testing levels that you can perform for testing an API are API security testing, performance testing, functionality, proficiency testing, API documentation testing, and Reliability and load testing.

Best API Testing Tools 

Postman Logo


Postman tool is a plugin in Google Chrome, and it can be deployed for testing API services. It is a powerful HTTP client to test web services. Postman is an ideal solution for testing API for manual or exploratory testing.

  • You can write Boolean tests with Postman Interface. 
  • With Postman, almost all modern web API data can be extracted.
  • For transmitting and receiving REST information, Postman is more reliable.
  • Unlike CURL, it’s not a command line-based tool, which makes this tool hassle-free of pasting text into a command-line window.
  • You can develop a collection of REST calls and save every call as part of a collection for execution in the future. 

Apigee Logo


Apigee is a cross cloud API testing tool. It enables the user to measure and test API performance and supports and builds API deploying other editors such as Swagger. It provides governance and security policies across all APIs. This automation tool has been named one of the top leaders in the 2019 Gartner Magic Quadrant for Full Lifecycle API Management four times.

Feature highlights

  • Identify performance issues by tracing API traffic, response times, and error rates
  • Easily create API proxies from the Open API specifications and use them in the cloud
  • Allows to design, monitor, and scale APIs

Karate DSL Logo

Karate DSL

Karate DSL is an open-source framework for API testing. The Karate framework is based on the cucumber library. Testers can test web services by writing tests in a domain-specific language with this automation tool. 

This tool is specifically developed for automated API testing and is released by Intuit. You do not need to have a programming language to deploy this tool. However, the basic understanding of JsonPath, XPath, JSON, and HTTP will be an added advantage. 

Top features

  • It supports the reuse of Payload-data for API testing 
  • Reports generation
  • It enables configuration switching
  • Multi-threaded parallel execution is supported
  • It helps create scenarios for API-based BDD tests in a simple way

Karate DSL allows you to write tests in any language which can deal with XML, JSON, and HTTP.

Tricentis Tosca Logo

Tricentis Tosca

Tricentis Tosca is a robust web services testing tool. Prominent API testing features of Tricentis are:

  • Enables end to end testing as API tests can be deployed across mobile, packaged apps, cross-browser, etc.
  • It’s one of the best API automation tools which utilizes model-based test automation that makes script maintenance simple.
  • It integrates into the Agile and DevOps Cycle.
  • This web services test tool supports a wide range of protocols inclusive of NET TCP, IBM MQ, REST, SOAP, TIBCO EMS, rabbit MQ, AMQP, JMS, HTTP (s)

Tricentis 400 (plus) customers include global names from the top brands like UBS, Telstra, Vodafone, Vantiv, A&E, Orange, Lexmark, Deutsche Bank, Starbucks, BMW, Allianz, Toyota, Whole Foods, HBO, and ExxonMobil. 

SoapUI Logo


Another on-premises API testing tool is SoapUi, enabling software development teams to test Web services, GraphQL, SOAP, and Rest.

SoapUI Pro is a complicated tool for analyzing, running, and creating sophisticated tests on web services for development and testing teams. SoapUI has many unique features, like test reports and SOAP testing. 

Pros of SoapUI

  1. SoapUI saves your work so that you can come back later.
  2. Without manual intervention, data can be sent from one response to numerous API queries.
  3. Groovy can be utilized to generate bespoke codes.
  4. The free package: Deploying the free package of SOAPUI, users can get full source codes and build their preferred features
  5. SoapUI allows reusability of scripts: Users can reuse their functional test cases as load tests and security scans in just a few clicks.
  6. Creating test is simple: just drag and drop

Cons of SoapUI

  1. There is no documentation for this tool
  2. Mobile app testing and web UI testing are ineffective

Rest-assured Logo


Rest-assured is considered one of the most effective tools for testing Java APIs. It is a Java Domain-Specific Language-based open-source tool. The Rest-assured API was developed to test web APIs so that you do not need to be an expert in HTTP. 

Pros of Rest-assured

  • Rest-assured supports the Given/When/Then syntax of behavior-driven development (BDD) testing
  • It has certain built-in functions, so you do not have to code everything from scratch
  • You do not need to be an HTTP specialist to perform this
  • Rest assured integrates seamlessly with the Serenity automation framework; therefore, users can combine the UI and REST tests in one framework that extracts excellent reports
  • Rest-assured is a popular rest API testing framework to test REST services in Java

Cons of Rest-assured

  • Rest-assured only supports Java programming language and does not expressly support SOAP APIs

ReadyAPI Logo


SmartBear offers the ReadyAPI tool for the functional tests, security, and load tests of RESTful, GraphQL, SOAP, and other web services.

In one intuitive platform, users will get four powerful tools: API performance tests, API functional testing, API & Web Virtualization, and API security testing. This tool will help you ensure end-to-end quality for all web services. 

It offers flexible automation options for integrating API testing into your CD or CI pipelines during every build. You will be able to create extensive and data-driven functional API tests.

Features of ReadyAPI 

  • ReadyAPI also offers features for getting rid of dependencies during testing and development
  • It provides features for reusing the functional tests and generating realistic load scenarios
  • The tool supports parallel execution of functional tests and job queuing
  • It supports command-line for automated testing
  • It offers native support for Axure, Jenkins, Docker, Git, etc
  • It has a Smart Assertion functionality that can create bulk assertions against numerous endpoints quickly
  • ReadyAPI can be integrated into any environment

ReadyAPI works best for DevOps and Agile teams. It is ideal for GraphQL, SOAP, Restful tests, security tests, functional API testing, and other web services.

Katalon studio Logo

Katalon Studio

Katalon is a popular test automation tool for APIs, web applications, and desktop and mobile apps. Katalon Studio supports SOAP and REST requests and offers multiple parameterization features and commands. In addition, Katalon follows a data-driven approach, supports CI/CD integrations, and enables testers to execute automated and exploratory testing. One of the most significant benefits of this software is that, regardless of its numerous beneficial features, it is not very hard to use, being suitable even for non-techies. 

Katalon provides an excellent and complete free package. Moreover, users can also opt for studio Enterprise (76 per month), which incorporates extended features and private plugins. As an alternative, the Runtime Engine package (54$ per month) further executes tests in CI/CD pipelines or through the command line interface. 

JMeter Logo


JMeter is deployed for functional API testing, which incorporates the need to test an API. JMeter is one of the best API testing tools, which has features that assist in boosting the performance of API testing.

Top features of JMeter 

  • It can automatically work with CSV files. This assists the test team in producing unique parameter values for API tests.
  • It supports the replaying of test results.
  • It can be deployed for both static and dynamic resources performance testing.
  • It’s minimal dependencies pycurl, pyyaml, optimally future) which enables easy development on-server for smoke tests or health checks


  • JMeter supports per-thread cookies
  • JMeter has a user-friendly interface that might be utilized in a command-line interface
  • It gives software developers the ability to replay test findings
  • JMeter can be used to test the performance of dynamic and static resources


  • In GUI mode, memory consumption is significant, leading to users receiving problems
  • It does not support JavaScript and, as a result, does not accept AJAX requests by default
  • It necessitates the user of experienced testers

Pyresttest Logo


Pricing: You can donate the amount by creating an account on GitHub.

Pyresttest is a python based tool for testing RESTful APIs. It is also a Micro-benchmarking tool. For APIs tests, it supports JSON config files. The automation tool is extensible in Python.

Desirable features

  • No code needed
  • Because of minimal dependencies, it has simple deployment on the server, which is helpful for smoke testing
  • The building of test scenarios with validates/extract/ generate mechanisms 
  • Return exit codes for failed results

Pyresttest is best for RESTful APIs.

Airborne LogoAirborne

The airborne tool is an open-source API test automation framework. It is a Ruby-based RSpec driven tool. This tool does not have a UI. It just offers the next file to write the code:

Key features

  • It can work with Rack applications
  • To use this automation tool, you must know Ruby and RSpec fundamentals
  • Airborne can work with APIs which are written in Rails

API Fortress Logo

API Fortress

What do you really check in an API tool from a testing standpoint? It should let you know if the API is up and running, and the second is the response time. API fortress satisfies both requirements and is ideal for API testing tools. This enables full API testing, including regression testing/ regression tests, and, like other tools, comes with functionalities such as SLA monitoring, reporting, notification, and alerts.

Fiddler Logo


Telerik developed Fiddler and has been a tool of choice for developers and testers who build and verify APIs exposed over HTTP(S). It is a free and powerful debugging tool deployed for testing restful web services. 

  • Fiddler’s API Composer makes it simple to test, organize quickly, and group your API requests.
  • Ensure the proper headers, cookies, and cache directives are transferred between the client and the server.
  • Debug traffic from Windows, macOS, or Linux systems and Android mobile devices and iOS
  • Supports any framework, including Ruby, Java, .NET, etc
  • With Auto Responder, responses and mock requests are effortlessly developed and organized, letting you test the websites without changing the code.

RedwoodHQ Logo


RedwoodHQ is an open source tool for testing SOAP/REST APIs and supports various languages, including Javascript/Groovy, C#, and Python.  It utilizes a web-based interface that allows various testers to execute tests on an application. This performance testing tool might be too shallow for developers. 

Pros of RedwoodHQ 

  • Connecting to open source automation tools such as Silk4J, Appium, Selenium, and others automates any user interface
  • An open-source framework for test automation
  • It allows the user to compare the outcomes of each run

Cons of RedwoodHQ

  • It is free and open-source, but it is also incredibly high-level and adaptable
  • The system is still not complete and not ready for production

Ping API Logo

Ping API

Ping API is an API testing tool that allows users to write test scripts in CoffeeScript and JavaScript to test APIs. It allows inspecting HTTP API calls with a complete response and request data. For any failures, you will get a notification via slack, email, or Hipchat. 


  • Ping API is one of the top API tools that validate CRUD flow and log in to Ping API.
  • Support writing scripts to set request body, headers, and URL parameters. Additionally, it supports writing scripts to validate response headers and body.
  • Ping-API to schedule tests every hour or minutes

Parasoft SOAtest

Build a foundation of API automated tests that can be executed as part of DevOps pipelines and continuous integration. Parasoft SOAtest automates the continuous testing of sophisticated systems by creating codeless API test scenarios from manual recordings. SOAtesr efficiently transforms your test artifacts into performance and security tests, reducing redundancy and increasing reusability. 

Top features:

  • Seamlessly integrates with load testing and service virtualization
  • Keep API test assets in sync with evolving systems through automation
  • Leverage artificial intelligence (AI) to create powerful test scenarios in less time
  • Automatically generate codeless API tears that are reusable and easily shareable

How to choose API testing tools

The number of API testing automation tools on the market for you and your team to try out and choose will possibly take forever. We have listed the critical considerations for you to keep in mind.

Complexity Ensures the skillsets in your team can learn and use the software in the shortest time possible.
Basic API requirements Does it support most of the HTTP requests? Can artifacts and settings be imported from one test/project to another to save time?
Interoperability Can the automation tool be connected to communication platforms such as Slack, project management systems such as Git, Jira for version control, or your team’s toolchain?
CI/CD integration Make sure you check its list of integrations to see if the platform works with CI systems your testing team is deploying, such as Bitbucket or Jenkins, and if it is native to avoid extra time attempting to configure everything.
Non-technical friendly Ensure you read the tools’ documentation to see if they support BDD conventions and can export easy-to-understand reports.

FAQS: Which is the best API automation tool?

best API automation faqs

Q: What is API?

A: Application programming interface is a collection of software procedures and functions through which other software applications can be executed or accessed. 

Q: What is the importance of the software test life cycle?

A: In agile development, every software development life cycle element is optimized for efficiency and speed. This is why testing too needs to be broken down in the software testing life cycle to ensure every component of the application has been verified in quality. 

Q: What are the basic features of API testing tools

A: The basic features of API testing tools are:

  • It has an easy to use UI.
  • Allows you to write tests even for the non-programmers
  • Supports various validation types and advanced validation expressions. Exhaustive features to rapidly validate your REST APIs.

Q: What are the benefits of APIs automate tests?

A: The important benefits of API automate tests are:

  • Content can be embedded from any site or application
  • Businesses can customize the service with ease
  • It helps you to personalize user experience
  • Businesses can update the workflow to become more productive

Q: Which are the Best API Testing Tools?

A: Here are some of the Best API Testing Tools:

  • Postman
  • Tricentis
  • HP QTP
  • Katalon Studio
  • Parasoft SOAtest
  • Eggplant
  • Subject7
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