One important thing I learned from my EET courses years ago ..... circuits have 2 responses to a change in voltage/current. There is an initial response that relates mostly to inductance and capacitance and previous state of circuit, then there is the 'steady state response' that comes after the circuit settles to constant state (micro/milli seconds later). That is not exactly referring to switch/contact bounce, but the interrupt could be triggered/cleared many times from contact bounce unless there is some kind of circuit that debounces the mechanical switch. One kind of test could be done is have the interrupt count/display how many times it gets triggered from a switch press.