9 Best Tools for API Testing

Eren Camlikaya
Eren Camlikaya 14 November 2020
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Most people these days are familiar with the term API, it is an acronym for Application Programming Interface. To briefly explain the API, its functionality is of a bridge that acts as an intermediary between two services or software applications.

Most IT companies are now preferring to shift their architecture towards Microservices and most microservices projects utilize API. As the user of APIs is becoming more and more essential it is really important to have some sort of performance checking or testing of these APIs, as whole software is depending on the results of these API calls.

As mentioned that API testing is very crucial so developers and programmers have to perform API testing. While the quality assurance of the software or programs is done by software quality assurance teams, API testing is a bit different in this aspect. API testing is carried out by the developers and in this process, it has been determined whether the developed API produces the desired results or not. It is essential to verify that it meets all the functional requirements and provides security and reliability to the application.

There is no Graphical User Interface (GUI) for the APIs so its testing can not be done on the front end. To perform the API testing, different software are used that sends calls to the API and in return get the output and the system response.

API Testing

Top 9 API Testing Tools

The need for API testing is now more than ever, with the right set of tools and solutions the API testing can be performed efficiently. There are hundreds of API testing tools available in the market. This article will provide a thorough analysis of the top 9 API testing tools, containing both open source and commercially available tools.

1. Katalon Studio

On top of the list, Katalon Studio take the place because of its great features and overall performance. The great thing about it is that it’s free of cost and it can be used to perform automation testing of API, web, and mobile apps. It provides all these frameworks and plugins in a single package which makes the development really easy.

Main Features
  • One of its best features is that it supports both Rest and Soap requests with commands such as GET, POST, etc.
  • It has support for a data-driven approach.
  • Automated and Exploratory testing, both can be performed.
  • It is a complete package and framework with a lot of builtin keywords.
Visit Katalon Studio

2. SoapUI

SoapUI is one of the best API testing tools for Rest and Soap APIs and It provides headless functional API testing. It is best in the scenarios when the API is quite complicated as it is solely dedicated to API testing. Top companies in the world like Apple, Microsoft, Oracle, etc are using SoapUI for testing APIs.

Main Features
  • It has Drag and Drop, point-and-click options which makes it very easy to use and fast.
  • It has a free and pro package, you can select according to your needs.
  • Groovy makes it easy for you to create custom code.
  • You can load data from databases and excel files.
  • It allows the reusability of the scripts.
Visit SoapUI

3. Postman

Postman was initially launched as a Chrome plugin, it has evolved with time and now is considered one of the top testing API tools. Postman has now become a platform for API development and it allows us to design, build, share, test, and document the API.

Main Features
  • It is very easy to use and can be quickly set up as a chrome plugin.
  • It is supported on Windows, Mac, and Linux platforms.
  • Supports both, Exploratory and Automated testing.
  • It supports CI/CD services.
  • You don’t need to learn a new language to use it.
Visit Postman

4. Rest-Assured

If you are looking for API automation, Rest-Assured is one of the best choices. It is a Java language domain-specific tool and if you need a framework to test Rest APIs in Java, then this is for you.

Main Features
  • It is an open-source platform.
  • You do not require to code from scratch.
  • It supports HTTP methods such as GET, POST, PUT, etc.
  • It is quite simple and even if you are not an HTTP expert you can use it.
Visit Rest-Assured

5. Apache JMeter

Apache JMeter is nowadays one of the most widely used functional API testing tools. It was initially developed for load testing but now widely accepted as a functional testing tool. It is an open-source tool with a lot of features.

Main Features
  • It supports both static and dynamic platform performance testing.
  • It comes with functionality to replay the test results.
  • Per-thread cookies are supported by JMeter.
  • It allows us to include the API tests in CI pipelines.
Visit Apache JMeter

6. Tricentis Tosca

If you are using the DevOps platform for development then Tricentis Tosca is the best choice for you. It is a customized continuous testing tool specifically designed for DevOps API testing.

Main Features
  • It can be integrated into the Agile and DevOps cycle.
  • With the use of model based test automation it maximizes the reusability.
  • Regression testing time can be reduced by using this.
  • It comes with a free trial option.
  • HTTP(s) JMS, SOAP, REST, Rabbit MQ, and many other protocols are supported by Tricentis Tosca.
Visit Tricentis Tosca

7. Apigee

Apigee is yet another amazing API testing tool by Google cloud. It provides the features to design, secure, publish, and test the APIs. Apigee features can be accessed using the other editors also.

Main Features
  • Performance issues are identified by tracking API traffic.
  • It has a single code based hybrid deployment model.
  • It supports Node.js and is powered by Javascript.
  • Open API Specification of proxies can be easily created.
  • It can be used to design, monitor, and scale the APIs.
Visit Apigee

8. Karate DSL

Another open-source tool for API testing is Karate DSL. One of its great features is that it helps us in creating scenario-based BDD tests very easily and does not require step definitions. These definitions are automatically created by Karate DSL which makes API testing very fast.

Main Features
  • It can be used with any JAVA program with standard test run and report generation.
  • It is easy to use and tests can be written without expert knowledge of JAVA.
  • It is built on Cucumber-JVM.
  • Multi-thread parallel execution is supported by Karate.
Visit Karate DSL

9. Assertible

The main focus of Assertible is on automation and reliability. It is an open-source tool and has recently been very famous among developers.

Main Features
  • Robust tests can be easily created.
  • It supports validating HTTP responses with turn-key assertions.
  • It has great support for the teams using the GitHub.
  • It has great features to quickly detect API issues.
Visit Assertible
Last words:

There are no such tools that fit in all situations and have all the required features. We have listed some of the top API testing tools and you can choose any of them according to your need and requirements.

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Eren Camlikaya
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Eren Camlikaya

Designing marketplaces for almost a decade.