The fog lamp nor the decat have ever been an issue on mine (emissions are the one thing it passes time after time)... what does it look like underneath?
Check the brake lines; are they corrosion free?
Body rust; if it's near any mounting points or on structural parts of the car, that's a fail. - Wire brush and Waxoyl usually gets that passed (unless you've got a hole).
Tyres; do they have plenty of meat left across 75% of the tread?
Brakes; do they stop the car and do you have meat on the pads?
Shocks/springs/coilovers; are they all working and not damaged?
Does your wiper clear the window (smearing is a fail)?
Exhaust; does it blow (fail), and it it excessively noisey (you can't technically fail for that, but they can refuse to test it thus you don't pass)?
I don't think the fact it's a Nissan dealer will have anything to do with it, but they might be a bit more open to reason about what constitutes "structural"; for example the box section is not a chassis rail, so it's not structural... but try getting your testor to believe that can be quite hard.