Motor test with or without usb connected?

The user docs say to:
connect apm, to comp using usb connection
then it says,
connect lipo battery

I was under the impression that connection usb and lipo at the same time results in the destruction of your usb port and a nice cloud of smoke. What am I missing here?

No it does not hurt it. I do it all the time without any problems.

just to clarify,
It’s ok to have usb cable connected and al;so have apm board powered by the apm power module at the same time. I assume that the other end of the power module can also be connected to 4 in 1 esc while usb is connected as well.

I always connect the usb first then I connect the lipo to the apm power module.

You need to connect the lipo to the PBD which feeds the ESCs that supply power to the motors for the test to be done. The motors are not powered from the USB.