SoapUI is a ReadyAPI tool you use to perform functional testing against your SOAP, RESTful, AMF, JMS or other API or web service.
SoapUI functional tests verify that an API or a web service follows the required business logic. In general, a test simply sends requests and checks if responses meet expectations. There is no need to examine how the service works, functional tests focus on what the service does.
Usually, the test consists of a number of requests or steps that simulate a real user behavior. On each step, assertions check that the service works as expected and returns the needed response.
By using data-driven loops, it is possible to reuse the same test steps with different data to make sure that the tested service handles it correctly.
Testers usually use functional tests during the entire service development. With functional tests, they verify that after adding new functionality to their applications, all features function properly. These tests can also be used in load testing.