How to validate calculation results?

GROMACS version: 2021.3
GROMACS modification: No

I wish to carry out integrator validation for my system, I was checking into this article and it was mentioned to carry out two calculations with different time step, however, I am not sure of the proper command to get the Hamiltonian fluctuations. How do we do this?

If there are tutorials that implement these then that would be great too!