An API or Application Programming Interface is a collection of software functions and procedures through which other software applications can be accessed or executed. In API Testing you use software to send calls to the API, get output and log the system’s response. For Agile development, Api Testing becomes important as shorter development cycles put more pressure on automated testing.

Here is a list of top Web Services Testing API Tools. The list contains both open-source(free) and premium web API testing tools.

1) TESTGRID

TestGrid API Testing is lightweight, web-based API development suite with a minimalistic UI design, which is 70% faster than the traditional API automation process to help you test faster and release better. You can engage your testing and business teams to build and execute test cases without any pre-requisites of programming knowledge.

Features:

• Easy to Use API Automation for SOAP and REST calls
  • Deeper Assertions — has the ability to write test cases that validate against API calls. Supports MITM
  • Fetch detailed report of the number of Source Type, Request Data, Response Data, Duration, Speed, Request Size, and Response Size.
  • Performance testing to help you optimize & improve your API
  • API Integration Automated Testing
  • Transaction Monitoring
  • Scriptless testing for faster automation
  • Integrate with your favorite CI/CD tool for continuous testing

2) KATALON STUDIO

Katalon Studio brings a hassle-free API testing platform for testers with or without prior programming experience.

Features:

• Supports all types of REST, SOAP requests, SSL client certificate.
• Easily import tests from Swagger (2.0 & 3.0), Postman, WSDL, and WADL.
• Built off of data-driven testing methods better test coverage and reliability.
• Create fluent assertions in BDD style with AssertJ support.
• Support set up API test data using UI testing.
• Provide insightful test report dashboards of all testing stages for better monitor and collaboration across teams.

3) Eggplant

Eggplant is the industry-leading test automation solution that provides true end-to-end API testing.

Features:

• Understand how the API behaves with both valid and invalid values.
• Easily add additional instructions and steps beyond simple API call and response.
• Discover and pinpoint anomalous behavior before your users encounter it.
• Auto-generate test automation assets by collecting and analyzing metadata by hooking into APIs.
• Combine API testing with validation of the UI to understand real-world performance and behavior.
• Easily build and execute API tests with pre-configured snippets, parameters, and SenseTalk scripts.

4) Subject7

Subject7 is a cloud-based, “true codeless” test automation solution that unifies all testing in a single platform and empowers anyone to become an automation expert. Supporting both REST and SOAP API testing and end-to-end and database testing, Subject7 makes it easy to scale and run sophisticated API tests through a simple and easy-to-use interface.

Key Features:

• Supports both REST and SOAP services
• Enables verification of responses in JSON and XML formats
• Reads and stores values from API response, easily incorporating them into the testing flow.
• Simple, non-metered pricing, delivering financial predictability.
• SOC2 Type2 compliant

5) Parasoft SOAtest

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

Features:

• Automatically generate codeless API tests that are robust, reusable, and easily shareable.
• Leverage artificial intelligence to create powerful test scenarios in less time than other tools.
• Keep test assets in sync with evolving systems via automation.
• Seamlessly integrate with load testing and service virtualization.

6) Postman

Postman is a plugin in Google Chrome, and it can be used for testing API services. It is a powerful HTTP client to test web services. For manual or exploratory testing, Postman is a good choice for testing API.

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

7) Tricentis

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

• This web services test tool supports a wide array of protocols including HTTP(s) JMS, AMQP, Rabbit MQ, TIBCO EMS, SOAP, REST, IBM MQ,NET TCP
• It integrates into the Agile and DevOps Cycle
• It is one of the best api automation tools which uses model-based test automation that makes script maintenance easy.

• Enables end-to-end testing as API tests can be used across mobile, cross-browser, packaged apps, etc.

• Tricentis’ 400+ customers include global names from the Top 500 brands such as ExxonMobil, HBO, Whole Foods, Toyota, Allianz, BMW, Starbucks, Deutsche Bank, Lexmark, Orange, A&E, Vantiv, Vodafone, Telstra and UBS.

8) SOAP UI

The most widely popular tool for API testing in the world, SoapUI allows you to test REST and SOAP APIs with ease — as it has been built specifically for API testing.

• Quick and Easy Test Creation: Point-and-click, drag-and-drop, functionality makes complicated tasks (like working with JSON and XML) simple
• Powerful data-driven testing: Load data from Excel, files, and databases to simulate the way consumers interact with your APIs
• Reusability of Scripts: Reuse your functional test cases as load tests and security scans in just a few clicks
• Seamless Integrations: Integrates with 13 API management platforms, supports REST, SOAP, JMS, and IoT

SoapUI Pro is used by thousands of leading companies around the world, including: Apple, Microsoft, Cisco, Oracle, HP, NASA, eBay, MasterCard, Intel, FedEx, and Pfizer

9) HP QTP(UFT)

It provides an extensible framework helpful in executing and building the functionality of headless system that do not have a user interface. It is one of the best api testing tools that helps to test the headless technologies like Databases and Webservices, JMS, etc. By using the API test conversion tool, you can convert soapUI tests to UFT (QTP) API tests.

10) vREST

vREST API testing tool provides an online solution for automated testing, mocking, automated recording and specification of REST/HTTP APIs/RESTful APIs.

• It provides an exhaustive tool to quickly validate your REST APIs
• This rest api test tool delivers zero defect web applications with less effort in API testing
• To validate your web application no skilled resources are required, and it can generate documentation for your API specifications
• API mocks can be created in vREST with the help of Mock Server Functionality. User can directly start developing frontend using mock HTTP requests

Source: Guru99