SoapUI is a widely-used open source testing tool that's been around for some time now. It's a powerful tool for testing web services, especially those that use SOAP, REST, and HTTP. It's highly flexible, allowing developers to create a variety of tests, such as load, functional, security, and compliance tests. It also makes it easy to create mock services for development and testing purposes. SoapUI provides a great platform for developers to quickly and easily create, execute, and maintain test cases. It's also easy to extend SoapUI with custom scripts and plugins, making it a great choice for developers who need to customize its features. With its robust features and open source nature, SoapUI is a great choice for developers who need to create reliable and comprehensive tests.