score:4
In theory, you should take two RAT (rapid antigen tests, or lateral flow tests) tests after you arrive in NZ, one on the day you arrive and one on day 5 or 6. RAT tests are widely available.
You should report the results of both tests to the Ministry of Health, who apparently will send you an email with all this info in anyway.
On a positive result, you should isolate, inform your accommodation, tourism company if using one, and the Ministry of Health.
However, you ask how this is enforced in practice, which is a slightly different question from theory.
It isnt enforced, you can report a negative RAT test result and no one will know. Isolation is done at home or in accommodation and no one enforces it, you wont get a visit from any official etc checking up on you.
NZ was very strict about Covid rules, yes - but this was during the period when community spread was trying to be eliminated. It largely worked for 18 months, allowing NZ to get vaccinated.
But since community spread started in August 2021, a lot of the rules are basically unenforced - theres no enforcement of mask rules for example, other than shop workers asking. Plenty of businesses have given up on that.
While we have an average of 5000 cases daily in the official statistics, most officials believe the number is much higher as people just dont report positive RAT results. There is no contact tracing any more, and you are no longer required to scan in or sign in when you visit places.