API (Application Programming Interface) testing is software testing where the APIs are tested on the message layer, such as the SOAP web services, REST API, etc.
APIs cannot be tested manually. Their functionality cannot be tested using the front-end, as there is no user in the interface. Hence, we need API testing tools.
API testing is particularly useful during agile development as the development cycles are short; thus, automated testing becomes the need of the hour.
What is API Testing Tools?
API is a computing interface that describes the interactions between two or more software entities. The API defines the calls and requests made from one system to another, how these calls are made, the format of data, the conventions to be followed, and more.
APIs have become important components of software development and require thorough testing for performance, functionality, security, and reliability.
Read also: Rest API Interview Questions
Why Use API Testing Tools?
Since all the application components are mostly loosely coupled, it is important to test the APIs. APIs reside in the business layer, which is likely to change many times. Through automated API testing tools, you can detect any format changes in request/response, or if there are any changes to the API itself, early in the testing phase. This simplifies the integration and regression testing phases, contributing to a shorter software testing life cycle.
API testing tools also perform load testing, reusability, scalability, security testing, and functional testing. Which API tool should you choose? Read on to see our favorite picks!
Best API Testing Tools
1. TestMace
Founded: 2018
Developer: testmace.com
Supported Platform(s): Windows, Mac, Linux
TestMace is one of the most powerful, modern, and cross-platform automated API tools that is useful for developers and testers. Developers can create complex mock scenarios and requests using authentication, variables, syntax highlighting, and autocomplete features. The UI is very simple to understand, and you can easily switch between environments. TestMace provides exhaustive documentation to support its features.
Testers can easily write test cases with the help of the tool’s graphics editor. The test cases can be tested with a single click! The tool also provides a JavaScript code editor to write complex custom scenarios.
Highlights:
- It supports a version control system and a well-organized project structure.
- There are different plans – the basic plan offers free API testing tools for commercial use and comes with most of the basic features a project would need. The other plans are individual, team, and enterprise.
- Embedded authentication methods.
- Autocomplete variable headers, syntax highlighting, protocols.
- Parameterized testing and debugging.
- Support for scheduling, reporting, analysis, bug tracking, and continuous integration.
2. Tricentis
Founded: December 2020 (Tricentis was developed in 2007)
Developer: tricentis.com
Supported Platform(s): Windows, Mac, Linux
Tricentis encourages automated testing, a completely codeless and AI-driven intelligent approach. It is a proven tool for cloud and DevOps and greatly enhances software delivery and the quality of enterprise applications.
Tricentis Tosca simplifies API testing by allowing testers to create API tests using a business-readable interface rapidly. It uses model-based API automation testing tools (i.e., creating an application model) to eliminate the need to write scripts. There are also productivity features like API scanning that enable users to build a test repository quickly with automatically versioned reusable assets. This makes the test cases resilient.
Highlights:
- Automatically identifies, manages, and eliminates test elements that trigger false positives.
- Zero or the very low maintenance of test cases – if the requirements change, the model needs updating once, and all the other changes are automatically synchronized.
- Easy to use for even non-programmers and non-technical persons.
- Integrates into the DevOps and Agile Cycle.
- Top brands like Toyota, Starbucks, Vodafone, and many more use it for API and end-to-end testing.
3. SoapUI
Founded: 2005
Developer: SmartBear
Supported Platform(s): Windows, Mac
SoapUI is an open-source, cross-platform API testing tool that allows testers to execute automated regression, functionality, load, security, and compliance tests. You can test all APIs, as SoapUI supports many standard protocols like SOAP/WSDL, JMS, REST, AMF, JDBC, etc.
It has a simple UI with drag-and-drop features, which even non-technical people can easily understand. It also supports debugging and allows testers to create data-driven test scenarios. Testers can also create their custom scripts (code) for complex scenarios. SoapUI can also be integrated with many popular automation tools like Maven, Junit, Hudson, etc.
Highlights:
- The commercial version is SoapUI Pro, and it has productivity features
- Built entirely on Java platform; uses Swing for UI.
- Core features include simulation, invocation, inspection, as well as functionality and security testing.
- Great tool for vulnerability testing and provides options to protect websites from hackers.
- Cloning feature that duplicates existing test suites to be put into other projects.
4. Airborne
Founded: 2016
Developer: RubyGems
Supported Platform(s): Windows
Airborne is an open-source framework to write automated tests for APIs. It tests APIs on top of Rspec and RestClient. Airborne is specifically for Ruby and provides simple response checks.
Airborne doesn’t have great documentation; however, it is easy to write tests, so you should be well prepared once you are familiar. It has no user interface other than a text file to create code and run the tests. But it's extremely accessible for even those who haven’t written any code before.
Highlights:
- Airborne can perform all of the mandatory tasks the API testing tool should do – assertion, chaining, wrapping, etc.
- It is used with RSpec, a Ruby Test framework used in Behavior Driven Development (BDD) groups.
- It’s a programming framework, thus easy to perform CI (Continuous Integration) and CD (Continuous Delivery) operations.
- Free and open source.
- Good for pair programming and extreme programming (collaborative) approaches.
Related Course
API and Web Service Introduction
5. JMeter
Founded: 1998; latest version 5.4.1 on 22-01-2021
Developer: Apache Software Foundation
Supported Platform(s): Windows, Linux, Mac (any environment that supports JVM)
JMeter is used for different types of testing, including load testing, functional testing, and unit testing. Its primary focus is web applications, and it can also be used for basic performance monitoring. JMeter supports many protocols and servers like HTTP, HTTPS, SOAP, LDAP, FTP, etc. It is open-source and available for free. Finally, JMeter has an interactive and easy-to-use UI.
Highlights:
- Platform independent, highly extensible.
- Supports multithreading framework to allow concurrent sampling by different thread groups.
- Stores test plans in XML format.
- Lots of plugins and extensions.
- Can be used with many programming languages like Java, PHP, etc.
6. RapidAPI
Founded: 2014
Developer: RapidAPI (Iddo Gino, Mickey Hasalvsky)
Supported Platform(s): Windows
RapidAPI is used for testing, design, monitoring, and much more. It has a very intuitive UX and supports any API type. Developers and testers can easily create detailed functional tests for deeper API validation. It provides centralized (global) monitoring and can be integrated into CI/CD pipeline. You can also use it to test all the REST APIs, SOAP, and GraphQL APIs.
Highlights:
- Developers can manage all the API interactions from a single place.
- You can sign up and try for a free account to see how the tool works.
- Cloud-based API testing tool for comprehensive testing.
- Users can view all the APIs connected to their accounts using the testing dashboard.
7. Postman
Founded: 2012
Developer: Abhinav Asthana
Supported Platform(s): Windows, macOS, Linux
Postman simplifies API testing and quickly integrates it into CI/CD pipeline, leading to faster development, testing, and monitoring. The Postman API development environment has three parts: collections, built-in tools, and workspaces. You can run requests, debug, test, create and document mock scenarios, and monitor the collections’ API. You can share the collections, assign permissions, and collaborate using the workspace.
Highlights:
- Basic plan is free and comes with all the necessary features for various team sizes.
- Supports various API call types like SOAP, REST, and HTTP and supports different data formats like RAML and GraphQL.
- Extensible and customizable through Newman, the command line collection runner
- Huge community support.
- Useful for developers, testers, and product managers depending on their needs and use case.
8. Apigee
Founded: 2010
Developer: Acquired by Google in 2016
Supported Platform(s): Windows, macOS, Linux
Apigee is an API gateway management tool to exchange data across cloud applications and services. It fronts services with a proxy layer, thus abstracting the backend service APIs.
Apigee has two main components. First, the Apigee services, which allow you to create, deploy, and manage API proxies. Second, the Apigee runtime, through which all the API traffic passes and is processed. The API monitoring is AI-powered, and thus, any issues can be identified in just a few clicks.
Highlights:
- Four plans – free version, team, business, and enterprise.
- Enterprise plan comprises all advanced features like Apigee Sense advanced security, traffic isolation, etc.
- Provides governance and security policies for all the APIs.
- Supports Node.js.
- Developers can easily track response times, API error rates, and much more through the customizable portal.
- One of the best tools for cross-cloud API testing.
9. ReadyAPI
Founded: Version 3.0 in 2019, version 1.0 was released in 2014
Developer: SmartBear
Supported Platform(s): Windows, macOS, Linux
Through ReadyAPI, you can test the functionality, load, and security of SOAP, RESTful, GraphQL, and many more web services quickly inside the CI/CD pipeline. It has a centralized interface and helps accelerate API quality for DevOps and Agile teams. Teams can create data-driven tests and add security scans easily with just a few clicks. ReadyAPI also offers virtualization of SOAP, RESTful, TCP, etc., and web services to remove testing pipeline dependencies.
Highlights:
- Interactive dashboard that quickly provides insights and metrics.
- Detailed reporting and analytics in various formats like HTML, CSV, etc.
- You can create synthetic data or import data from various data sources and share it. Data for different types of tests like load, functional, security, etc., to check boundary conditions with realistic data.
- It is essentially a paid version of SoapUI developed by SmartBear – it has all the features of SoapUI and more.
10. REST-assured
Founded: First release (1.0) in December 2010
Developer: Johan Haleby
Supported Platform(s): Windows, macOS, Linux
REST-Assured is a Java-based DSL through which you can write readable and powerful tests for RESTful APIs, but not OAP APIs. It is a Java library, so integrating with Junit, TestNG, or other Java frameworks is easy, and integrating to CI/CD is also very fast. The code is in human-readable form (like English) as it supports Given-when-then notation similar to if-else.
Highlights:
- Supports data-driven testing and authentication mechanisms like basic username-password authentication and OAuth authentication.
- Provides support for all HTTP methods without the need to write the boilerplate code for setting up HTTP connection, sending requests, and parsing the response.
- Open-source.
- Offers many other features like XPath validation, specification reuse, easy file uploads, etc.
- Works best for JSON response type.
Bonus: Katalon Studio
As a bonus, Katalon Studio is worth mentioning in our list. Katalon LLC developed a dual interchangeable interface to create test cases, like script view and manual view. This means both technical and non-technical persons can use it.
It follows the Page Object Model pattern, wherein an object repository is created for web UI elements captured using a recorder app.
Katalon Studio has three versions: free, enterprise, and runtime engine so that teams can customize based on their budget and operational needs.
Conclusion
All the above API testing tools are good in their own ways, and we cannot say one is better than the other. The API tester you choose depends on your business case and the features that your project requires.
Now that you have an idea about some of the best API testing tools, it’s time to upgrade your software knowledge! Explore Top 10 Software Testing Courses.
