Forget politics and religion. If you want to know the real moral fibre of someone important to you, stand next to them at the supermarket.
Not only will you figure out your compatibility levels on all sorts of deal-breakers such as trim vs full fat and free range vs caged, you will also get the chance to see how they treat the checkout chick.
Believe me, how they treat the checkout chick is all you need to know.
We've all been standing in line having a sneaky read of Woman's Weekly when some pompous git in front has got hot under the collar about a bruised apple or the price of milk and taken it out on the girl packing his bags.
It's almost as offensive as the more common sight of shoppers who manage the entire process of packing and paying without once looking the clerk in the eye or saying hello.
The benefit of working as a teenager in menial jobs is that I learned early that people on minimum wage have brains, too.
This will come as no surprise to those carefully wrapping our frozens and swiping our Eftpos cards, however, given the way some people treat those in the service industry, it's clear not everyone thinks this way.
When the chips are down and the stress levels high, some of my best conversations are the light and airy ones I have with the checkout chick on the way home from work.
The connection is brief, the conversation pleasant and the subject usually refreshingly light (with the odd exception such as the time at checkout 10 when I mistakenly asked how the assistant's day was going and stood there watching my icecream melt as she regaled me with the unsavoury details of her unravelling marriage).
As much as I enjoy chatting to the checkout chick, I'm also always keen to embrace new technology, and so after months of suspicion and curiosity I finally plucked up the courage to try out Pak'n Save's automated self-checkout facilities.
Designed for those with only a couple of items but used by idiots like me with far too many, the automated machines scan the barcodes of your products, weigh your fruit and vegetables, prompt you to swipe your Eftpos card and basically do everything for you bar raising and educating your children.
It seemed neat.
But like most of my encounters with technology, the love affair was short lived.
The honeymoon period ended when the machine kept trying to pass my avocados off as aubergines and the relationship soured further when the barcode reader wouldn't follow its job description and read the barcodes.
Those items that I did manage to scan eventually spilled over the sides of the capture area where they are weighed to prevent theft and eventually the spectacle of me chasing errant tomatoes over the floor caught the attention of the checkout chick on hand to help fools like me that couldn't help themselves.
As she patiently processed my purchases and explained slowly and patiently (a little like you would to an especially dim child) that the item limit was there for a reason and it was best to weigh and label the tomatoes in the vegetable section first, I fell in love.
She was kind, she was informed, she understood my frustration and, best of all, she was not a machine.
Automation may have certain efficiency gains and undoubtedly it is the way of the future but, as long as the thing processing my groceries remains a human being, I shall take every opportunity I can to talk to her because the only conversation I could have with the self-checkout machine was the one-way kind with all sorts of language I can't reproduce here.
Eva Bradley is an award-winning columnist.