LVDS cable - Impedance measurement
First, note that we're talking impedance, rather than resistance, so you can't just put an ohm meter on it to check.

Differential impedance will depend to some degree on frequency, so it's necessary to measure at the frequency which you expect to encounter, and preferably higher in order to give some safety margin.

The only way to test the cable is to send an LVDS signal through it and monitor the received signal. Make sure the receiver is properly terminated, and use a signal at the same data rate which you will be using.