What Are the Best Free Open Source Testing Tools, Frameworks, and Libraries by@katalon

What Are the Best Free Open Source Testing Tools, Frameworks, and Libraries

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Free open-source frameworks, libraries, and tools are the go-to solutions for automation testing.

The main difference between these is knowing your preference between building a brand new test automation framework using libraries or working with a made-ready tool where testing is all you will have to care about.

This article gives you a quick glance at the Top 10 Free and Open Source Testing Tools, Framework and Libraries.


Katalon Studio


Katalon Studio is a popular and free test automation tool for web, mobile, API and desktop (Windows). Offering both low-code and scripting methods, Katalon Studio removes the complicated training to build and maintain a separate testing framework.

With everything built-in, users can focus directly on testing activities and spend less effort on creating, running and maintaining tests.

Feature highlights:

  • Supported programming languages: Java and Groovy
  • OS compatibility: Windows, macOS and Linux
  • Flexible and fast test creation with Record and Playback, Manual and Script Mode
  • Debugging UI and smart reporting to troubleshoot failed testsReusable test artifacts (test cases, objects, keywords, etc.) with the Page Object Model (POM) design and Test Artifact Sharing
  • Supported testing methodologies: BDD, DDT, Keyword-Driven Testing, Cross-Browser Testing (Headless, Chrome, Edge, Firefox and Safari) and Cross-Platform Mobile Testing (iOS, Android)
  • Allow importing Selenium, SoapUI and Postman projects
  • Native integrations to CI/CD systems (Jenkins, Bamboo, Azure DevOps, CircleCI, etc.), ALMs (e.g. Jira)
  • Step-by-step tools training to use Studio in real projects on Katalon Academy



Selenium is probably the first name that pops up on the subject of web-based and open-source test automation. To be more exact, Selenium wouldn’t be considered as a tool, but an open-source library.

With the field-famous trifecta of Selenium WebDriver, Selenium IDE, Selenium Grid and the recent release of Selenium 4, this is sure to be the top choice for coding enthusiasts.

Feature highlights

  • Supported programming languages: Java, JavaScript (Node.js), Groovy, Scala, PHP, Perl, Python, Ruby or C#
  • Import advanced tests scripted on Eclipse, Visual Studio or NetBeans
  • Compatible with macOS, Windows and Linux for cross-platform execution
  • Customizable add-ons and plugins
  • Allows integration with frameworks such as Ant, Maven, TestNG, JUnit, NUnit, etc.

Website: https://www.selenium.dev/



Sharing a similar suffix as Selenium’s, Appium is likewise the open-source framework to remember for mobile automated testing. From native, mobile web to hybrid applications, Appium is a highly sought-after option to eliminate the need for recompiling applications and automating APIs.

Feature highlights

  • Supported programming languages: Java, PHP, Objective-C, C#, Clojure, JavaScript with Node.js, Python, Perl or C# whichever Selenium supports
  • JSON Wire Protocol to add flexibility to the programming language used
  • Automated testing scripts can run on iOS and Android platforms
  • Test applications without having the source code in place

Website: https://appium.io

Apache JMeter


Apache JMeter, or JMeter in short, is an automation tool for performance (load and stress testing) and functional testing. JMeter’s primary uses are to measure the performance of applications and act as virtual users to send requests to the designated server.

Feature highlights

  • Supported programming language: Java
  • User-friendly UI/GUI and Beanshell processor for custom code
  • Works with HTTP, HTTPS, JDBC, LDAP, FTP, LDAP, SOAP, POP3, IMAP, SMTP, TCP, and Java-scripted protocols
  • Open to integrating with Jenkins and third-party reporting tools
  • Multi-threaded framework (Concurrency Thread Group) to sample functions separately from a thread group

Website: https://jmeter.apache.org



To test SOAP and REST APIs, we got SOAP UI. Aside from API testing, SoapUI’s open-source application for web service testing additionally covers functional, load, compliance and mock testing.

Feature highlights

  • Supported programming languages: Groovy and Javascript
  • Protocol support for SOAP/WSDL, REST, and JMS
  • DataSource TestStep for Data-Driven Testing
  • Simple requirements management
  • Integration with Maven, HUDSON, JUnit, and Apache Ant

Website: https://www.soapui.org

Robot Framework


Using Python as the main scripting language, Robot Framework is an open-source framework for acceptance testing and robotic process automation (RPA). The Robot Framework is commonly associated with free mobile and desktop applications testing tools.

Feature highlights

  • Supported programming language: Python, Jython (Java), PyPy, and IronPython (.NET)
  • OS compatibility: Windows, macOS, Unix, and Linux
  • Can use Eclipse, RIDE (Robot Framework IDE), or text editors to build tests
  • Keyword-driven testing, autocomplete completion and syntax highlighting to reduce coding time
  • Integration with Appium and Selenium

Website: https://robotframework.org



Watir, or Web Application Testing in Ruby, provides you with open-source libraries in Ruby for cross-browser or web test automation. Watir uses Selenium under the hood, so it’s able to utilize Selenium’s common API.

Feature highlights

  • Supported programming language: Ruby
  • Browser compatibility: Chrome, Firefox, Edge, Internet Explorer, Safari
  • BDD design available from integrations with Cucumber, RSpec, etc.
  • Watir 7.0.0 is available on RubyGems, but requires Ruby 2.6+ and Selenium 4.0

Website: https://watir.com



Java plus unit testing give us JUnit. Ranking 7th in Java Top 10 Libraries, this free open-source testing framework is a favorite among Java developers to edit and refactor code at the unit level. What’s more, the release of JUnit 5 has brought useful updates like better organizing tests in hierarchies, simultaneous use of multiple runners at once and more.

  • Supported programming language: Java
  • Script automated unit tests with annotations and assert classes
  • Extension APIs or extension mechanisms to work with third-party software
  • Parallel execution (version 5.3 onwards)
  • AssertThrows method for easier exception and timeout handling

Website: https://junit.org



Often referred to as the “Selenium for Android,” Robotium is a popular open-source framework for Android applications black-box testing, both native and hybrid.

  • Supported programming language: Java
  • Run-time binding to view all Android UI components and activities
  • Integration with Gradle, Maven, and Ant to write automated mobile tests
  • Adjustable execution speed with Config.sleepDuration and Config.sleepMiniDuration

Website: https://github.com/RobotiumTech/robotium



Our last open-source test automation framework is Citrus. Citrus would definitely ring a bell for developers working with integration testing and verifying messaging transport connectivity. As well as that, connecting JUnit or TestNG to use in complementary is common to script Java-based unit tests.

  • Supported message protocols: HTTP, REST, SOAP, Kafka, JMS, etc.
  • XML or Java coding for flexible test creation
  • Integration with Apache Camel, Arquillian, Kubernetes and Docker to enable microservice integration
  • testing BDD and cloud-native BDD automated testing using Cucumber and YAKS

Website: https://citrusframework.org

Katalon Studio or Open-Source Frameworks?

In case you’ve been thinking about which is the best tool to choose – don’t.

With the cost out of the picture, it’s not a good idea to say what is best without giving the context.

  • What’s your team trying to test? Is it web, mobile, API, desktop or many at once? You can’t expect a unit testing framework to also cover the requirements of functional testing.
  • Are the developers taking care of the testing as well? If the responsibility of developers in your team involves both developing and testing software, then you’re geared up to build your own test automation framework. But if it’s largely QAs, then Katalon Studio will help free up your developers to focus on building software, features, custom keywords and testing on the lower levels such as unit and integration. In turn, your QAs will be the ones taking care of the larger-scope testing like end-to-end.
  • Will the tool help my team scale effortlessly? This is key. Integrations to ALMs, CI/CD, DevOps and Agile toolchains, without a doubt, will be needed when your teams grow. For open-source frameworks, every new integration with a third-party tool will require workarounds. Yet, Katalon Studio’s integrations are all native. You can be rest-assured to connect in a few clicks and get back to testing right away.
  • Will updating to the tool’s latest version require additional work? If you’ve been using Selenium 3.x, then upgrading to Selenium 4 isn’t as simple as clicking “Upgrade Now.” Instead, you’d have to migrate every single test and test suite. And while that’s happening, there would need to be someone still taking care of the existing tests and updating the failed ones. In contrast, Katalon Studio is as easy as clicking “Upgrade Now” for you to enjoy to newest features and improvements instantly.

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by Katalon @katalon.Katalon is the leading low-code test automation solution for Web, API, Mobile, and Desktop apps.
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