The UltraESB allows the creation of Mock Services for almost any protocol over multiple transports. Thus you can mock REST, SOAP, Hessian, or even JMS, Email or File/FTP related services, or even other such services easily.
The article "Mock RESTfully with the UltraESB" shows how one may write Mock services for REST methods GET, POST, PUT and DELETE.. The mock service implementation can be written as Java as a class, code fragment or a Spring bean, or as any JSR 233 Scripting language code. However, you do NOT need to compile, bundle, deploy any of these - as the UltraESB does all that automatically! Just checkout the sample and see how a dozen lines of configuration can simplify your tasks!
The AdroitLogic ToolBox will allow one to test the mock services, as well as any other backend services. It includes sample RESTservices, a RFC 2616 compliant HTTP/S client that supports basic and digest authentication and 2-way SSL in addition to supporting GET, PUT, DELETE, POST, HEAD and OPTIONS for REST.