In-N-Out Burger might be a good fast-food equivalent to Apple. I have no idea if they focus test any of their food but they've had the same menu for ages. They do a few things very well, and there's also a mystique about the company.
I doubt In-N-Out focus-tests, as they never really change anything, but there are a number of other parallels to Apple. They have a near-religious focus on the customer experience, to the point where they pass up significant growth opportunities (like franchising) rather than put that experience at risk. Not to mention that the frenzy around the opening of a new In-N-Out makes an Apple Store opening look positively sleepy.
Their focus on the customer experience may actually be religious. They discreetly print bible verses on food wrappers and cups. Maybe they couldn't trust normal people to uphold their Christian affiliation.
The bible verses were introduced in the mid-1980s when the then-president of the company went "born again" (as it was still a family-owned/family-run business at the time, this was easy to implement by fiat). I suspect their continuing presence has more to do with inertia than any evangelical bent at the corporate level; removing them would stir up negative PR with no real purpose.
The creepy thing about In-N-Out is that nearly every In-N-out store is exactly the same. Overall I've been in probably 20-30 that all use the same layout with very small differences (placement of the ketchup station, sometimes fake plants in dividers and a couple variations of placement of a few seats). As well as a few kitchen variations but I haven't noticed those anymore.
