Deuteronomy 13:3 Can Christians explain this verse. Why would God need to test our love?

I thought I remember reading elsewhere in the Bible that God does not test....only Satan does....and that God sometimes uses Satan to "rinse" us (i think that was the term describing how we are given hardships to teach us and toughen us). God knows everything, so why would he need to test to see if he loves us? That's something that humans do and when humans do it, if doesn't feel fair. It's not open and honest. It feels deceptive. So please...Only serious Bible reading Christians respond please. Thank you.