To test if someone is being loving, or faking it, one could use the below "official bible definition". ;). (often read out at weddings which is pretty important for people deciding to spend decades together)
"1 Corinthians 13:4-8 NIV
Love is patient, love is kind. It does not envy, it does not boast, it is not proud. It does not dishonor others, it is not self-seeking, it is not easily angered, it keeps no record of wrongs. Love does not delight in evil but rejoices with the truth. It always protects, always trusts, always hopes, always perseveres. Love never fails. "
I think 2 obvious bits of this missing when people fake it are "it is not self-seeking" (just like you said) and "rejoices with the truth". I don't think it's that hard to tell, or rather, if its hard to tell if someone is being loving or not, then unfortunately they probably aren't.
My 2p.. YMMV etc ...