Loving those who are not lovable, that's actually not easy. Perhaps that's why it is considered the true test because loving the lovable comes with great ease and you can't but just love them. But giving love and not expecting a return, loving someone when they are in their worst state, that's out of the ordinary truly and is very commendable.
It's the true test because it's harder to love those who are not loveable...those who don't even love themselves deep enough. It's a hard task but that's the true test of love.