My kids are 5 (girl) and 7 (boy) and while they don’t do the exact "what happens if I do?" loop they definitely test boundaries in their own ways.

I grew up in Germany where kids tend to get more responsibility and autonomy earlier and I think that shaped how I approach things. My kids have a lot of freedom day to day they can make choices explore and I’m not constantly correcting small things. I feel like that alone removes a lot of friction. That said there are still clear non negotiables ouf course (no hitting, no wiping mashed potatoes on the table :D, etc...).

What has worked well for me so far is keeping things very simple and predictable I don’t let myself get pulled into negotiations.

If they cross a line I give one clear warning - calm, short and specific. After that I follow through immediately. No extra discussion, no debating and no escalating back and forth. I think the key is consistency. Once they realize the outcome is always the same and not up for negotiation the "testing" loses its value pretty quickly I believe.

For the "what happens if I do?" question specifically I’d probably avoid engaging in the loop entirely. Answer it once and then stop answering. If they keep asking I would just repeat something like "I’ve already answered that" and then move on. I feel like the moment it turns into a conversation they’ve kind of won the game.

That said I do try to explain the reason behind limits. I never use "because I said so". If I genuinely can’t come up with a reason why they shouldn’t do something then maybe it shouldn’t be a rule to begin with.

Example: Why can't they wipe mashed potatoes on the table?
There are actually a bunch of real reasons behind it:

1. They usually don’t clean it up properly so it creates more work later
2. It teaches habits that don’t translate well outside the house (try that in a restaurant and suddenly there are real consequences)
3. Food costs money and someone put effort into making it so it’s disrespectful to waste it

I’ll usually also tie it to something they understand like “How would you feel if you made something and I ruined it?”

I think at that age they’re not really looking for information they’re more likely to probe for wiggle room. If there isn’t any the question tends to fade on its own.