Never, ever do something you have no intention of carrying through on. Your lack of enthusiasm will probably bleed through and using other people for personal gain isn’t the nicest way to be known. People talk, and it would suck blowing an interview and losing a job because of such talk.

I would apply to jobs that I would be happy to get in case my boss decides to decline the raise anyway.

Small counter-opinion here; if I interview a candidate, offer them a role, and find out that they have been using our time only to get a better deal from their current employer, then I will most likely choose not to interview them again in the future.

If you have engaged with me in bad faith (pretending to want a job with us when you actually don't) then I would be very uncomfortable endorsing you to join one of my teams in the future.

By all means, interview around. And if you get a better offer and accept it, then I will cheerfully congratulate you and wish you the very best of luck! But if you're operating in an area where the pool of potential employers is small, make sure you don't burn too many relationships in the process.

And how would you find this out? People do get counter offers, some even accept them. It's part of the game. No need to be petty.

In one case, the same person did the same thing to us twice in a row - interviewed, got an offer, then got "counter offered" from their existing company the next day. Pretty confident that they're just interviewing as a negotiating tactic.

But honestly, in general, if someone interviews around then decides to stay at their existing company for more money, they're probably not the folks I'd be likely to hire regardless. They're not looking for new learning opportunities, or new ways to grow, they're maximizing for some other value structure. And best of luck to them with that, I'm sure they'll find plenty of companies where those values are the expectation and norm.

You're "playing the game", but I build teams out of folks who aren't game players. :)

This is a bit unethical, but the candidate in question could just say that their current employer gave them a newer, better offer that they couldn't refuse, essentially giving plausible deniability. Though I do agree that the interviewer would be fully in their right to not re-interview the candidate.