In cali, we pinch off the hose at the canister that goes to the tank, screw a special cap onto the filler neck and attach a hose that fills it to pressure with nitrogen. at a specified pressure it looks for leakdown.
Have someone with a smoke machine inject smoke into the hose at the canister into the fuel tank, remove the fuel cap until you see smoke, then put the cap on and look for the smoke.
Or, drop your tank and look for cracked hoses, if none, follow the hose to the canister, if thats OK, look at your filler neck hose and filler neck.
We dont functionally check the EVAP purge valve or canister, those are visual.
Regardless, if you dont do it right, have a shop do it right. If we find anything wrong we will fail it. Cali is getting HARD on us smog techs, and sending alot of undercover cars through our shops so we cannot miss anything.