API Testing is a software testing technique which ensures if the developed APIs meet the desired expectations. In this article, you’ll find the top Open Source/Free API testing tools which would help you to perform API testing with ease, effectiveness and without paying any money from your pocket.
API testing has become a major area of Quality Assurance in the recent times. Main focus of automation testing has always been on UI testing. But trends are changing and there is an increase in demand for API testing through automation. Earlier, APIs were mainly tested manually but with the emergence of so many effective tools brought the solutions into the hands of automation testers to test the APIs through automation with ease.
As we know, UI tests are slow and depending on them solely can kill the automation efforts. That’s where API testing comes. These tools play a great role in helping to deliver the product in the market on time with high effectiveness and productivity.
Let’s figure out; which tool would fit best for your need and testing requirements.
Rest-Assured is an open-source Java based library to test HTTP based REST services.
It is designed to make API testing simple and it seamlessly integrates with any existing Java based automation framework.
- Supports BDD Gherkin (a non-technical, human-readable language) Given/When/Then syntax.
- Has a bunch of baked-in functionalities, which means you don’t have to code things from scratch.
- Integrates flawlessly with UI automation testing framework, so that users can easily combine the GUI and REST tests all in one framework.
- Users don’t need to be an HTTP expert.
If you are looking for a Java solution to test APIs, I would strongly suggest Rest Assured. In my overall experience of API testing, it has always been my main tool.
Pricing: Open Source
Initially, Postman came up as a Chrome Browser extension. But now Postman has native applications for Mac and Windows operating systems.
- Postman is perfect for exploratory testing.
- It is a very Easy-to-use REST client, has a very clean and rich interface. Because of this reason, it is a very comfortable tool especially for beginners and could be the first choice to start learning API automation testing.
- Has a bunch of integrations like support for Swagger & RAML formats.
- It enables users to easily share their knowledge with the team by packaging up and share all the requests and expected responses.
Pricing: Free – PRO $8/user/month and Enterprise $18/user/month
SoapUI is present in the market for quite sometime and it’s been quite a popular tool among automation testers.
It is a fully functional tool to support API testing with ease and it is built with dedication to support both REST ans SOAP APIs. If your team is working on complicated API, then SOAPUI can be a good choice to start with.
- In free package, users can get the full source code and can build features of their preference.
- It’s easy to create test using Drag and drop, Point-and-click operations.
- Re-usability of Scripts: load tests and security scans can be reused for functional test cases in a just several steps.
- In situations, if you need to write custom code, you can easily do that using Groovy.
- Powerful data-driven testing: Data loaded from files, and databases, and Excel so that they can simulate how consumers interact with the APIs.
- Support creation of complex scenarios, native CI/CD integrations and asynchronous testing.
Pricing: Free – $599/year
Katalon Studio is automation testing tool to support Web UI functional, API/Web services, and Mobile testing.
Katalon Studio provide support for SOAP and RESTful service requests with various types of commands (GET, POST, PUT, DELETE) and provides parameterization capability.
- Support both SOAP and RESTful API testing.
- Provide hundreds of built-in keywords for writing test cases.
- Provide support for AssertJ, one of the most powerful assertion libraries to create fluent assertions via BDD style.
- Suitable for both pros via custom scripting using Groovy and non-techies via Manual.
- Support API, Web GUI and Mobile testing all at one place.
- Support data driven testing approach.
- It can be used for automated and exploratory testing.
- Provide CI/CD integration support.
JMeter is an open-source tool. Built for load testing but it is widely popular among the testers for functional API testing as well.
QA engineers can take great benefit out of this tool as it provides all sorts of functionality which are required to test an API.
- JMeter automatically works with CSV files which allows the team to quickly create unique parameter values for API tests.
- JMeter supports integration with Jenkins which means we can include API test in CI pipelines.
- JMeter supports both static as well as dynamic resources performance testing.
Pricing: Open source
6. Karate DSL
Karate DSL is pretty new API testing tool in the market and helps to write scenarios for API-based BDD tests quite simple. One of the advantages is that you don’t need to write step definitions unlike other BDD frameworks like Cucumber, JBehave etc. exclusively.
- It is built on top of Cucumber JVM.
- Tests are easy to write even for non-programmers.
- It supports multi-threaded parallel execution.
- You can generate reports just like any other standard Java project.
- If you are already using Java and Cucumber in your project, then KarateDSL might be a great choice.
Pricing: Open Source