Guy I’m seeing tried to test me because he thinks I’m cheating

though I’ve never given him a reason. He brings it up all the time and it’s starting to wear me down.

The other day he actually tried to test me. He had one of his friends message me in a flirty way, like it was some setup to see what I’d do. I realized what was going on right away and shut it down, but it honestly bothered me that he even thought that was okay.

Now I’m questioning if this is just immaturity or if it’s a big red flag. What do I do here?