http://www.repair-home.com/Using_a_Circuit_Tester_to_Test_a_Switch
well that good the switch isnt dead..something simple sometimes overlooked ...i just looking at the diagram you made ..if you put one end of tester on one end of the yellow line ,and one on the other ,,it should light up as your doing nuthing but making sure the wire is good completing a circuit [check for a broken wire itself].one of those wires shouldnt make the tester come on until you turn the switch on.to test the switch ,youll just need to do the hot poll that shoots electricity into the machine ..when its off the light shouldnt be on ,,,when you turn on switch ,then it should light up showing a complete circuit ,power is going through that wire into machine
The linker above shows testing a switch to see if your power is OFF so you can work on a switch in your home ,,,your doing same thing only other wire .
if nuthing else someone that dosent know how to do this may learn.
i dont know i always use an ohm meter ,by no means am i tryigng to make anyone look stupid ..i know how people can take commennts on here and i dont want to be the bad guy here ,honestly trying to help .