The Best API Testing Tools
Tags: testing
Published: 2023-01-18 16:30:05

An Application Programming Interface or API enables two software to talk to each other and share data. Testing APIs ensures the software quality and helps developers understand if the product is ready for release. Hence, testing APIs is crucial. Here are a few [mobile app testing](https://www.headspin.io/solutions/mobile-app-testing) tools you can consider.

**Katalon Studio**

Initially released in January 2015, Katalon Studio is an automation tool with a Selenium-based engine. Katalon helps reuse and create automated test scripts for UI without coding and allows running automated tests for elements like pop-ups, wait-time, iFrames, and more. You can launch Katalon Studio on macOS, Linux, and Microsoft Windows.

Katalon is a free solution. However, in 2019, they also released an enterprise version and a Katalon Runtime engine to help customers get flexible options to meet their various requirements. The free solution with the basic functionalities is still available for use.

The main advantage of Katalon Studio is how easy it is to deploy and has a broader set of integrations compared to Selenium. Developers with different programming skill-sets can seamlessly use Katalon’s dual scripting interface – helping testers with limited knowledge of writing code to efficiently use its interface.

**HeadSpin and Katalon**

HeadSpin integrates with Katalon Studio to provide comprehensive API testing solutions. HeadSpin lets you connect to real devices worldwide. Automation enables you to run API tests and maintain app consistency on all your devices. Additionally, test real user experiences anywhere in the world, on multiple devices, networks, and operating systems.

Katalon Studio lets you connect to remote devices, enabling you to utilize Katalon Studio testing suites to leverage HeadSpin’s device infrastructure. To test any application, you will need a Cloud Application ID. With HeadSpin, you can use a wildcard value instead and specify this in your app capabilities.

**API testing**

Katalon Studio allows you to test APIs without additional integrations. Due to this, testers can use it to perform effective end-to-end API tests, maintain their tests, and automate scripting. This module’s main features include code inspection, references, debugger, code snippeting, and code auto-completion. Katalon Studio’s software supports all SOAP/1.2, SOAP/1.1, and REST requests, also various data sources like databases that have a dynamic mapping to help increase test coverage, XML, and XLS.

Katalon’s API testing mode lets users import tests from API editing and testing tools like WSDL, Swagger, and Postman. It also has an inbuilt response viewer that allows testers to auto-format and search for access to artifacts.

**Feature highlights:**

- Katalon has an Easy-to-use UI and comes with productivity-centric features for all types of projects.
- It supports SOAP requests, SSL client certificates, and REST.
- It helps with Native CI/CD integrations like CircleCI, Dockers, Jenkins, Azure DevOps, and more.
- Uses UI testing to support API test data.
- Katalon enables test imports from WSDL, WADL, Postman, and Swagger.
- It offers free tool tutorials and API testing courses.
- Its data-driven testing methods help developers test reliability and coverage much better.
- It provides AssertJ support to help create BDD-style fluent assertions.
- Katalon also has a built-in reporting platform that allows centralized reports and activities.

**Pricing:** Free — $76/license/month

**Postman**

Postman is an API development tool helping developers test, modify, and build APIs. It contains a comprehensive list of functionalities that developers can use. Many developers use this tool each month as it keeps development easy. Postman can make HTTP requests like POST, PATCH, GET, and PUT. Developers can also use it to save environments for later use and convert the API code for multiple languages like Python, JavaScript, and more.

**Feature highlights:**

- Postman comes with a rich interface.
- It is available for both exploratory and automated testing.
- You can run Postman on Linux, Windows, and Mac.
- Easy-to-use REST client.
- It offers monitoring, documentation, testing, and run features.
- It provides integrations like support for RAML and Swagger formats.

With Postman, users can easily share knowledge with their team by packaging up the expected responses and requests and sending them over to their colleagues.

Developers can also use Postman’s advanced preferences to help organize API elements and collections like monitors, documentation, mock servers, and tests – generated from API schemas. You can also use Postman to manage your team’s public data and share links to requests, APIs, and Requests from the Postman app.

**Pricing:** Free – $12/user/month

**Apache JMeterTM**

Apache JMeter is an open-source software developed by Stefano Mazzocchi to measure performance and load functional test behavior.

**Open-source Tool**

Developers use the Apache JMeter, an open-source testing platform, to run performance and load testing.

**Cross-platform Testing**

You can use JMeter on any platform that has a JVM like Linux, macOS, and Windows since it is solely Java-based.

**Smooth API Testing**

JMeter comes with easy, seamless, and quick API testing capabilities.

**Quick Scope Tests**

JMeter is a powerful performance testing tool that makes running tests easy for experienced and inexperienced testers.

**Enables Load Testing**

JMeter effectively measures a web application’s capability to meet a specific load requirement.

**Enables Stress Testing**

It also effectively measures the stress of an application under heavy workloads.

**Plugins**

JMeter comes with a comprehensive list of plugins. Additionally, you can install more plugins from the plugins manager.

**Feature highlights:**

- Cache and offline replay of test results
- JMeter is available for both static and dynamic resources performance testing
- Able to include the API tests in the CI pipeline thanks to JMeter and Jenkins integrations
- Automatically work with CSV files, thus enabling the team to create unique parameter values for the API tests at speed

The recent versions of JMeter have plenty of new features and enhancements like bug fixes, revamped library, JMeter functional testing templates update, new themes, visual representation of disabled elements, and bug fixes.

**Assertible**

Assertible is an API [testing and monitoring tool](https://www.headspin.io/enterprise) that developers can use to help validate and test your web application.

Assertible can help you use reliable code for your teams and customers.

Their documentation provides a complete guide on getting started with using Assertible.

**Feature highlights:**

- Assist in running API tests after deployments and integrating with familiar tools like Zapier, GitHub, and Slack.
- Support automating API tests throughout CI/CD pipeline
- Help testers update their tests when their specifications change with The Sync feature. Hence it’s needless to manually update tests after adding new parameters or changing the response of the API
- Support validating HTTP responses with turn-key assertions

Assertible added new features, like the Encrypted variables feature, which developers can use to store tokens, secret data fields, and passwords. Assertible aims to improve the security practices around API testing.

**Pricing:** Free – $25/month