Can I earn money playing games as international student in UK?

I think the title says it all.

What kind of games are we talking about? Gambling? Video games? Russian roulette?

It is. The more important question is: how good you are at gaming or gambling? the latter is very risky: you can win or lose everything.

video games. There's a place you can test games and earn some money

Hi, it's actually like me testing some games and getting some money. If I do it one time, would it be an issue?

I can't think of anything that prohibits you from earning money that way. Student jobs are pretty common for internationals as well, although I'm curious of what you're referring to. It's the first time I hear of someone earning money by testing videogames.