How to test waters with a guy at work being subtle?

I kind of have a crush on a guy from work but we do not talk that frequently. Only when we happen to bump into each other or if we are eating together as a group. Personally I think as long as I’m working there it would be hard to pursue anything since everything is formal. Also he's usually quiet. Any advice on this?
How to test waters with a guy at work being subtle?
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