How do you test an idea before talking to users?

Genuinely curious: what’s your “first-mile” approach before you book those early interviews?

Do you start with Reddit deep-dives? Reverse-engineer reviews? Talk to personas in your head?

I’ve been experimenting with ways to simulate early conversations using real user chatter - trying to shortcut the phase where you waste 5 interviews learning what the internet already knows.

Would love to hear how others approach this. What’s worked? What hasn’t?