2004 325CI no cr4ank issue

I have a 2004 bmw 325ci with a no crank problem. Turn key to start and dash lights up but doesn't crank. Took battery and had load tested..good. Assumed it was the starter and bought a new one. Had the new starter tested twice before i installed. Turned key to start and same thing happened. Double checked all connections..all clean, tight and correct. I don't know how to test if power is getting through ignition to small wire running to starter. I did use a multimeter to check for dc volts on the small wire by connecting black probe to a good ground and red to the small wire. Turned key on and got zero volts. Turned key to start and still got zero volts. Just not sure I tested it right. At this point I'm thinking ignition switch...key cylinder...key. No idea how to test ignition switch. Any help would be greatly appreciated with explanation on how to do it. Thank You

2004 325CI no cr4ank issue