Years ago I was told there’s an easy way to test if someone has aphantasia: ask them how many windows are in their home. They might ask if windows in doors or windows that leads into other rooms count and you can tell them yes or no because the answer doesn’t actually matter.
Once they tell you the answer ask them how they came to that number. The majority will say they imagined standing in each room and looked around. People with aphantasia will either say they don’t know because they never counted them, or that they know they have three rooms facing an outer wall so there must be at least one window in each of those rooms or another method that used logic rather than imagination.
This isn’t meant to out someone as having aphantasia or anything like that. It’s just a handy method if someone is wondering if they have it, or a fun little exercise between friends with no judgement. You can even do the test on yourself and quickly work out if you have to use imagination or logic.