Iron Test is described as 'API test automation tool that has GUI, supports HTTP stubs (mock services), data driven testing, and API types beyond HTTP, such as relational database, JMS, FTP(s), AMQP, MQTT, etc' and is an app. There are more than 25 alternatives to Iron Test for a variety of platforms, including Windows, Linux, Mac, Online / Web-based and SaaS. The best alternative is Insomnia REST Client, which is both free and Open Source. Other great apps like Iron Test are Postman, Hoppscotch, soapUI and Advanced REST Client (ARC).
Postman is a tool that facilitates the development and use of APIs. Postman provides all the functionality needed to create or simulate API specifications and use the Postman Collection Runner to create tests.
Katalon Studio is a free and robust automation solution for API, Web and Mobile testing. It eliminates the complexities of building an automation framework by integrating all necessary test components with built-in keywords and project templates.