What tests can I conduct on someone that’ll reveal how they feel about me (e.g. whether they like/dislike me, find me entertaining/annoying)

This person doesn’t really reveal the way they feel. They often give emotionless vibes. I would like to know how they feel because it will give me an idea of whether I should continue approaching them or not.

p.s They are often on their device and I find it quite awkward to approach them because sometimes i don’t know if I will be “interrupting” whatever they are doing. But I do want to know for once and for all how they feel. Asking them is not an option since this person isn’t the type who will give a direct honest answer (also we are not close enough for them to be that honest, I believe they’ll feel uncomfortable if I do ask) , the only thing that I can do is test them while observing their reactions/actions.