She smell checks almost every ingredient and never tastes. Best cat. Then she smells the end product and we're both like 'that's that done, then'.
Pretty much all the time. Whenever my cat is staring at me and I have something in my hands, if he's close enough to sniff, I hold it where he can sniff. Doesn't matter what it is.
If it's food, and maybe the food is something he is interested in, I can see his expression/posture change, and I pull back and and separate a small, cat-sized bite for him to try, being careful to only give him cat friendly morsels, like a piece of meat or something.
Usually he doesn't have any interest in what I'm eating, so that's rare. Most of the time he sniffs, then retreats to a safe distance, uninterested in what I'm having... I just think he's not sure until he gets a good whiff; so I give him one.