Top 6 Open-source API Tools for Software Companies in 2024

API Testing (API) is a software test type that decides whether the established APIs fulfil the application’s availability, usability, efficiency, or security expectations. According to Google Trends, the interest in testing API/web services has been rising gradually in the last few years. 

In 2019, 91% of respondents had or intend to have a structured API tools process in place shortly, according to a study carried out by SmartBear in over 3372 app specialists for API testing framework. 

Around 45% of API testers indicated that their company automated more than 50 percent of test projects. More than 75% of companies around sectors still consider API efficiency a top priority. API automation testing is more important than ever with the right method, tool, and approach. 

API checking is a vital aspect of the efficient practice of the CI/DevOps. This article would sum up the top API tools for open source and commercial solutions that testing teams use to meet their needs.

Top API Tools for Testing

Below are the API tools for testing:

1. Katalon Studio

Katalon Studio is a free API, Network, Laptop, and Smartphone tool for test automation. It is being developed as a leading platform to test API and Web services and is positioned for developers and testers as an advanced end-to-end automation solution. 

With different types of commands and parameterized functions, Katalon Studio supports SOAP and REST requests. A particular aspect of Katalon Studio among the top API tools is integrating user and API/web services with a range of applications (Windows, Mac OS, and Linux).

Feature highlights:

1. SOAP and rest support Support
2. All-in-one shop with and the integrated features of API, WebUI, Desktop Software, and Mobility trials.
3. A data-driven approach is supported.
4. Can be used for automatic and scanning experiments
5. CI/CD integration helped.
6. AssertJ, one of the most powerful library for claims, supports fluent claims in the BDD format.
7. For non-technology as well as technical using Manual and Groovy Scripting modes.

2. SoapUI

SoapUI is a headless API testing framework for users to monitor REST, SOAP, and Web Services APIs quickly.

Free package: Users can obtain the full source code and develop their favorite features with the free SOAPUI package.

1. Drag and Drop, point and click test quickly and easily
2. Scripts reusability: load checks and protection scans can be repeated in just a few phrases for practical test cases

Pro package:

1. Databases filled with images, databases, and Excel to model how customers communicate with APIs efficient data-driven research
2. Native CI/CD integrations, asynchronous experimentation are assisted.

The new SoapUI 5.6 launched in July 2020 modified and deleted non-used third-party libraries (org.apache.HTTP components, commons-logging, commons-codec, & JUnit) (Jackson, Keene). SoapUI now disables the project scripts Load and Save by default to increase testing protection.

3. Postman

As a Chrome browser, Postman now expands the Mac and Windows approach using the native version. For those who do not want to use the same language as developers in an advanced programming environment to cope with coding in Postman, API test tool checks a safe option.

1. REST consumer ease of use
2. Rich and quick to use interface
3. Users can use it for both automatic and for exploratory experiments.
4. You can run on Mac, Windows, Linux, and Chrome applications.
5. Has a range of integrations such as Swagger & RAML formats support
6. Has functionality running, checking, documentation and tracking
7. Do not need new language learning.
8. Enable users to express the information quickly and to their peers to process both requests and planned answers.

From version 7.3 in 2020, Postman allows users to easily arrange the collections and APIs created from new advanced preferences from API schemes (mock servers, displays, tests, and documentation). The latest update, 7.31.1, was released with slight error corrections for the Mac, Windows, and Linux App in August 2020.

4. Tricentis Tosca

Tricentis Tosca is an ongoing Agile and DevOps testing framework. Tricentis Tosca’s advantages include:

1. Help several protocol arrays: HTTP, AMQP, Rabbit, TIBCO EMS, TOAP, REST, IBM MQ, TCP Net Supports many protocol arrays:
2. Requires the Agile and DevOps cycles
3. Maximize reuse and repair with model automatic testing
4. You can use rest API test framework checks for mobile, cross-browser, bundled applications, etc.
5. Achieving new technologies sustainable workflow
6. Reduce regression research time
7. Interactive tests allow test managers to conduct manual tests and obtain data without Tosca environments being designed.

The first edition of self-healing SAP modules was released in the new version 13.3 revised in June 2020. When LDAP Authentication Support is introduced, these releases will boost Mail Engine 3.0.

5. JMeter

JMeter is used extensively for practical API testing but is developed for load testing.

1. Enables the replay of test results
2. Function with CSV files automatically so that the team can easily build specific API test tool parameter settings.
3. By integration between JMeter and Jenkins, users may include API testing in CI pipelines.
4. It can be used for performance checking of both static and dynamic properties.

JMeter 5.3 has been full of various features and changes since the previous edition in May 2020: New themes, The redesigned Groovy catalog, A range of bugfixes, A graphic view of the components disabled, Revised JMeter models for practical research, etc.

6. Karate DSL

Karate DSL is a rest API test framework test tool that helps build API-based BDD scenarios easily and unwritten. KarateDSL has provided these concepts to allow users to kick-start the API tools easily.

1. Build Cucumber-JVM on top
2. Can run a test and produce reports such as every Java standard.
3. Without any Java material, a test may be written.
4. And non-programmers can write tests easily.
5. Supports switch/stage setup and multi-threaded execution in parallel

Karate UI has been a standalone Maven artifact from version 0.9.3 and is not part of the foundation of an open-source tool. The integrated support for WebSocket based on async capability is also included in this edition. 

The new August 2020 Karate UI 0.9.6 update included numerous updates: Windows Desktop app automation – Robot Karate Windows, modified HTML reports, single-cache calls, and enhanced UI tree walking.

Conclusion

We assume the above list provides the right approach if we intend to take API tools. But discovering the right one-tool to achieve all this, as with other applications in this field, is virtually difficult. Some may think the commercial players’ characteristics sufficiently, but ownership costs are a significant aspect. 

Open-source options are cost-effective but require qualified resources and efforts to incorporate the required system. Tools appearing to be a relative compromise of costs and other considerations could have limitations for such project forms to be taken into account.

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