The goal of this work is the development of a tool capable of automatic test generation for GUI applications in the GNOME desktop environment. The tests are generated using metadata provided by the assistive technologies, specifically the AT-SPI. The proposed test generator utilizes the given metadata to create a model of a tested application. The model maps the event sequences that are applied on the tested application during the test generation process. The generation process involves the detection of severe bugs in the tested application. The results of the test generation process are automated test cases suitable for regression testing. The functionality of the implemented test generator was successfully verified by testing 5 open-source applications. The testing of applications performed by the proposed tool has proven the ability to reveal new bugs.