The Master’s thesis focuses on testing REST API interfaces of web applications. The result of the thesis is the Restty application, which allows to test API endpoints of said interfaces, as well as to create extensive test cases from the interface’s endpoints. The theoretical part of the thesis explains the principles of web services, remote interfaces, technologies that are used for development of the application, and the Swagger framework upon which the application is built. Subsequently, the design drafts of the application are presented in detail. The following section covers Restty’s implementation and demonstrates how the Restty can be used for testing the interface of a Red Hat JBoss BPM Suite application. In conclusion, the benefits of the Restty application are evaluated and its possible extensions are proposed.