SoapUI
SoapUI is a free and open source cross-platform functional testing
...This is for developers and testers looking to accelerate their ability to deliver REST, SOAP, and GraphQL APIs. SoapUI Open Source is the simplest and easiest way to begin your API testing journey. APIs, or Application Programming Interfaces, have become the center of software development, connecting and transferring data and logic across disparate systems and applications. Luckily, testing them can greatly improve the efficiency of your testing strategy as a whole, helping you deliver software faster than ever.