This is indeed confusing, but it will have to wait until the debugger interface is improved in order to catch the button press event by the user. Currently the debugger just quits the application, which to the testing tool looks like the application died.

There is still a way to stop the whole execution. If you display the testing tool while debugging, there is a progress bar at the bottom right indicating the debugging progress of all tests. To the right there is a stop button which allows you to stop the execution for all tests.