The easiest way to test or simulation ground noise or CM noise is with a series generator using a CM choke. We used to use an audio and RF power amp., brushed motors twisted along cables, and large inductive pulses.
But you could also use a square wave using dry NC contacts in series with power relay coil.
But you should read the standard.
You can even inject a CM 6kV lightning bolt with 30 ns rise time. Use 100 ohm series R into an ideal CM transformer as CM.
A typ. Transformer is not as balanced as a CM choke which requires 0.1% tolerance to suppress 60dB , then the Pi filter provides the LPF breakpoint. check the specs. A typical iron transformer power supply attenuated 70 dB for lightning on a linear DC output with a line filter. SMPS supplies vary widely.
Go fetch Fully Understanding CMRR in DAs, IAs, and OAs
Analog Applications Engineer-Precision Linear TI site