def trigger_system_testing(self):
        """Trigger system testing session.

        That is, if at least one test case was chosen.
        """
        if not self.chosen_cases_listbox.items:

            create_and_show_dialog(
                "At least one test case must be chosen.",
                level_name='info',
            )

            return

        ### grab test cases ids

        test_cases_ids = [
            LABEL_TEXT_TO_TEST_ID[item]
            for item in self.chosen_cases_listbox.items
        ]

        ### turn on a flag for saving the test settings for reuse
        ### after the tests are finished
        APP_REFS.system_testing_set = True

        ### trigger system testing session

        raise (

            ResetAppException(
                mode='play',
                data={
                    'test_cases_ids': test_cases_ids,
                    'playback_speed': self.speed_entry.get(),
                }
            )

        )
Trigger system testing session.

        That is, if at least one test case was chosen.
        
nodezator/editing/playback/systemtesting.py